AWUS01 KWNH 051926
FFGMPD
NYZ000-PAZ000-MDZ000-VAZ000-WVZ000-OHZ000-060045-

Mesoscale Precipitation Discussion 0226
NWS Weather Prediction Center College Park MD
323 PM EDT Mon May 05 2025

Areas affected...portions of northern Mid-Atlanitc and central
Appalachians to Lake Erie

Concerning...Heavy rainfall...Flash flooding possible

Valid 051846Z - 060045Z

SUMMARY...Training of showers and thunderstorms from the northern
mid-Atlantic and central Appalachians to the southern shore of
Lake Erie may result in isolated to widely scattered areas of
flash flooding through the early evening. Rainfall rates of 1-2
in/hr are expected.

DISCUSSION...Visible satellite and regional radar imagery from
1830Z showed scattered showers and thunderstorms extending from
northern VA into northern MD, northwestward into PA, western NY
and eastern OH. These showers/storms were located northeast of a
closed mid to upper-level low over the OH Valley with low level
southeasterly flow advecting moisture northwestward across the
region. Broadly diffluent flow aloft was in place to the northeast
of the closed low, helping increase synoptic scale lift over the
region. Blended TPW imagery showed that PW values ranged from ~1.4
inches to the southeast over northern MD to ~0.7 inches over
eastern OH. SPC mesoanalysis data from 18Z showed MLCAPE was
generally weak at 500-1000 J/kg with cloud cover or lower moisture
values limiting instability to some degree.

However, flash flood guidance values across a large portion of the
region were about 1.0 to 1.5 inch/hr or slightly less and
similarly oriented low level and mean steering flow wind vectors
were supportive of repeating cells. While 925-850 mb winds were
generally weaker than the mean steering flow, low level axes of
confluence will support lines of showers/thunderstorms with a
tendency for cell repeating and short term training. The
environment is supportive of 1-2 in/hr rainfall rates and some
indications from the RAP support a minor increase in the low level
flow toward 00Z which could help increase the threat for
backbuilding cells. The flash flood threat is expected to be
isolated to widely scattered in nature through 01Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7ash_-YrVg9-HmJOfkJNSKwXzW6mVwXXl1y78FanFERR4KeCRFwGXVp981GV7fwADlFJ= wMa5Jxe3gm5I0s6RlRrAnhs$ for graphic product...

ATTN...WFO...BUF...CLE...CTP...LWX...PBZ...RLX...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 42437874 41107743 40007715 39257740 38697812=20
38777907 39138020 39888046 40198103 40628153=20
41728134 42258003=20

=3D =3D =3D
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AWUS01 KWNH 052239
FFGMPD
PAZ000-MDZ000-VAZ000-NCZ000-DCZ000-WVZ000-060300-

Mesoscale Precipitation Discussion 0227
NWS Weather Prediction Center College Park MD
638 PM EDT Mon May 05 2025

Areas affected...portions of eastern VA into the DMV and far
eastern WV

Concerning...Heavy rainfall...Flash flooding possible

Valid 052235Z - 060300Z

Summary...Training convection will be capable of hourly totals of
1-3" with short-term (3-hr) totals as high as 2-4". Isolated to
scattered instances of flash flooding are possible (and may be
locally significant in sensitive urban/mountainous terrain).

Discussion...Radar and GOES-East satellite imagery indicate the
proliferation of convection across portions of eastern VA/NC over
the past several hours, moving fairly rapidly (~25 kts) towards
the N-NE within nearly unidirectional flow on the eastern
periphery of a large, deep layer (850-200 mb) closed low centered
over IL/IN/KY. The mesoscale environment in the vicinity and
downstream of the aforementioned convection is characterized by
SBCAPE of 1000-2000 J/kg, PWATs of 0.8-1.3" (between the 75th and
90th percentile, per IAD sounding climatology), and deep layer
(0-6km shear) of 20-40 kts (per 22z SPC SFCOA analysis). The
strongest cells have been capable of impressive instantaneous
rainfall rates of 3-5"/hr (per MRMS estimates), which has resulted
in estimated hourly rainfall totals of up to 2.5" (where deeper
convective cells have been able to occasionally train, mainly to
the east of I-95 in eastern VA).

Recent hi-res CAMs have not handled the evolution of convection
particularly well, and recent observational trends (including
continued overshooting/cooling cloud tops via GOES-East imagery)
suggest that localized hourly totals of 1-3" will continue to
manifest farther north (into the more sensitive DMV region) with
storm propagation (as a pool of 1500-2000 J/kg of SBCAPE remains
untapped). While both of the hourly updating CAMs (HRRR/RRFS) are
handling the convection poorly, the 18z HREF suite does still give
a good idea of the potential for excessive rainfall through 03z
(with 40-km neighborhood probabilities for 2" and 3" exceedance of
20-30% and ~10%, respectively). Given locally sensitive terrain
(per FFGs as low as 0.75-1.50" and 1.50-2.50" for 1-hr and 3-hr
periods, respectively) over urbanized terrain along and near I-95
and over portions of the Appalachians in the vicinity of northern
VA, western MD, and far eastern WV, isolated to scattered
instances of flash flooding are possible (and may be locally
significant, should 2-4" totals occur over the most sensitive
localities).

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6dfyBFfZ7lIgNjsTCMzn8e7-k6qb3VAuAVNx0xL5na-fLggLrUtAcLowcrkE6wezFkVC= SbWHtIKcv95cd5dDCOkUzKI$ for graphic product...

ATTN...WFO...AKQ...CTP...LWX...RAH...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON 39827743 39597667 39037647 37767669 36447699=20
36217739 36777738 37437742 38277778 39617833=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 060247
FFGMPD
TXZ000-NMZ000-060830-

Mesoscale Precipitation Discussion 0228
NWS Weather Prediction Center College Park MD
1047 PM EDT Mon May 05 2025

Areas affected...Central & Eastern NM...Cap Rock & Northern
Permian Basin of TX...

Concerning...Heavy rainfall...Flash flooding possible

Valid 060245Z - 060830Z

SUMMARY...Streaks of thunderstorms with repeating flanking line
development will become increasingly efficient with moistening
profiles. Increasing rates to 1.5-1.75" with 1.5-3" totals
resulting in widely scattered incidents of possible flash flooding.

DISCUSSION...GOES WV continues to show fairly static deep upper
low across east-central AZ with trof extending southward as
stronger 120-130kt 250mb jet undercuts it resulting in broad
downstream diffluence across the Southern High Plains into W TX.=20
An embedded vorticity center can be seen near the SW Heel of NM
starting to sharpen, ready to lift northeastward providing even
further mid to upper level forcing through strong DPVA. As a
result a strong 995-6 surface low exists in the vicinity of the
Davis mountains with a strong 50-60 Td gradient across it in less
than a few miles. This dryline extends north toward an
intersection with old stationary front between CNM and GDP (which
extends along the Sacramento Mtns toward ABQ and southeastward
across the Pecos Valley toward ECU/ERV. Isallobaric response in
the lowest levels is supporting very strong convergence along the
axis of both the dry line and stationary front providing very
solid moisture and instability transport, with 40-50kts of
southeasterly flow off the Rio Grande Valley into the W Texas
Panhandle; PWs are trickling into the 1.25" range and capped 2000+
J/kg CAPE (a subsequent MPD may be required if/when cap breaks
across southern Permian/Pecos River Valley).

North of the front/dryline intersection, flow is backed further
out of the east-northeast to northeast at similar 20-40kts from
surface to boundary layer. The flux into the front is pooling to
.75-1" PW and support a narrow ribbon of 1000 J/kg as far north as
ABQ. As such, strong thunderstorms have been developing along the
stationary front and given deep layer steering, have been lifting
north (further west) and northeast (across the northern Permian
Basin to southern Cap Rock).=20

Given the upstream forcing remains upstream, the surface response
has locked the front and these localized convergence maxima to
support back-building or flanking redevelopment that generally
follow similar paths. Initially, large hail and gusty winds have
been the primary factor, but the continued flux and rainfall has
been locally moistening the profile and increasing rainfall
efficiency. Combine this with continued expanding divergence
aloft, upscale growth into clusters and 'wedges' in satellite
appearance will increase, though the source/redevelopment regions
will decouple as the DPVA and FGEN ascent lifts north and
northeast. As such, rates up to 1.5"/hr will become possible and
with training/repeating, streaks of 1.5-3" will become more likely
across north-central NM into the Cap Rock.=20

AHPS 7-10 precipiation anomalies show much of these areas have
seen well above normal rainfall (200-400%) and NASA SPoRT 0-40cm
soil saturation graphics denote this as well rising into the
70-80th percentiles, especially further north and east across the
Cap Rock into the Big Country. As such, scattered incidents of
flash flooding should become possible through the overnight
period.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6PKildUX1RhiAHTlcMe9ccRmpalpVifABwVk08lPLvwyKfNKcyUYuNQJlLxz22CWuTJS= wc46mBXOFov0C6cHXb7mjyE$ for graphic product...

ATTN...WFO...ABQ...AMA...LUB...MAF...SJT...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON 36450534 36050360 34950147 34260051 33360001=20
32649996 32180013 31740065 31700321 32100423=20
33790521 34500562 35210638 36040636=20

=3D =3D =3D
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AWUS01 KWNH 060507
FFGMPD
TXZ000-060930-

Mesoscale Precipitation Discussion 0229
NWS Weather Prediction Center College Park MD
107 AM EDT Tue May 06 2025

Areas affected...Stockton & Edwards Plateau of Western Texas...

Concerning...Heavy rainfall...Flash flooding possible

Valid 060505Z - 060930Z

SUMMARY...Continued risk of regenerative thunderstorms along the dryline/surface front. Deep layer steering may support
training/repeating locally for streaks of 2-3" totals and possible

DISCUSSION...GOES WV suite depicts very deep (3-3.5 Std. Dev.)
closed low generally centered in the Lower Colorado River Valley
and is currently reorienting as very strong shortwave energy
rotates around the western to southwestern edge of current center.
This is elongating the overall low favorably across eastern AZ
into much of NM to support strong divergent/diffluence pattern
with 100-120kt jet streak rounding the base of the upper-low in NW
Old Mexico. In also supporting/broadening updraft strength for
any convection that does develop, it is has be strengthening solid
moisture return through the Rio Grande and Pecos Valley through
the southern High Plains. Strong easterly and confluent
southeastern flow at 15-20kts exist across much of north-central
to southeast NM.

CIRA LPW denotes deepest moisture remains upstream across the
western TX panhandle through the Guadeloupe Mtns with nose of
.5-.75" sfc-850mb wedge trying to filter in. Concurrently, the
850-700mb layer from the southeast on 35-40kts of flow (per VWP)
is reaching .5"...reaching near 1" totals across southeast NM.=20
EML's are steepening lapse rates to support sufficient lapse rates
to support 500-1000 MUCAPE pooling along the stationary frontal
boundary toward a surface low in the northern Rio Grande Valley
north of ONM. As such, orographic ascent and localized
convergence is sparking widely scattered thunderstorms in the
vicinity of the frontal zone. Weak isallobaric pressure falls aid inflow/maintenance of updrafts for a few hours to over-come the
strong effective bulk shear in the weakly unstable environment.=20
As such, steering flow in diffluent pattern supports short-term
training of the updrafts oriented more south to north across
northern NM, while more SW to NE in the vicinity of the Sacramento
Range into eastern NM. Rates of .75"/hr and 1-2 hours of
repeating, may support localized totals of 1.5-2.5" and given
dry/hard ground conditions has the potential to exceed the lower
FFG values (1-1.5"/hr, 1-2.5"/3hrs).=20

Eventually, shortwave energy will round the base and the
associated jet will increase southwesterly flow and the frontal
zone will start to lift east and northeast with further enhanced
moisture flux convergence along the leading edge. This should
help to expand overall coverage, but may limit the increased
duration locally into the early morning hours. Isolated incidents
of flash flooding remain possible through morning.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_N5fE4wFHlpDy96aRX6nu7dP0VdlmSqvAb_Yw_c5WL_QNHt1YAOzA3rEqzY6z0l5Je8t= xE_-6y1JfoCsrcGbzSqoLFg$ for graphic product...

ATTN...WFO...EWX...MAF...SJT...

ATTN...RFC...WGRFC...NWC...

LAT...LON 32369992 32079938 31449903 30729857 30019832=20
29339841 29129956 29160073 29750195 29830241=20
31290348 31600310 31720173=20

=3D =3D =3D
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AWUS01 KWNH 060556
FFGMPD
NYZ000-PAZ000-061100-

Mesoscale Precipitation Discussion 0230
NWS Weather Prediction Center College Park MD
155 AM EDT Tue May 06 2025

Areas affected...Central PA...West Central Upstate NY...

Concerning...Heavy rainfall...Flash flooding possible

Valid 060555Z - 061100Z

SUMMARY...Additional 1-2" of rainfall in 1-2 hours across recently
saturated soils and low FFG pose possible localized flash flooding
over next few

DISCUSSION...GOES-E WV shows an eastward extension of the deep
upper low, extending across WV into central MD providing increased
downstream DPVA ascent and a localized increase in low level WAA
across MD into central PA. 05z surface analysis shows the cold
front remains fairly banked up along the front range/Blue Ridge of
the Appalachians into central PA connecting to a triple point
south of BFD, with warm front bisecting PA just north of SEG
toward the Lehigh Valley. Along with the slight increase in LLJ
to 30kts, increased low level moisture is bringing back 1.0-1.25"
total PWats and some weak instability about 250-500 J/kg. Solid
southwesterly flow along/behind the cold front further strengthens
FGEN ascent through the area. As such, recent RADAR and 10.3um
EIR show increasing shallow convective cells across the
Mason-Dixon line from RSP to DMW, but extend northward through
much of the warm sector in central PA.=20

Deep layer steering along/ahead of the cold front will support
training of cells; with 1"/hr rates, so with length supportive of
1-2 hours of training across a narrow axis. This may result in an
additional 1-2" in less than 2hrs across areas that already had
some heavy rainfall this afternoon, especially further north into
south-central NY. The combination over saturated ground
conditions and 1-3hr FFG values of .5-1.25 and .75 to 2,
respectivly; suggest flash flooding may be possible through the
remainder of the overnight period.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-8E8PW1DctycXKrVsVpd_vZmgHagG0EasYre2KnqTLi3IRhMNVCwo-EnfuHBRiQU2hY5= 2uceGZ-a4oCqFIZwB6JsG6Q$ for graphic product...

ATTN...WFO...BGM...BUF...CTP...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 42997787 42947738 42617691 42077658 41467649=20
40697655 40457662 39757688 39907774 41387840=20
42187861 42717843=20

=3D =3D =3D
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AWUS01 KWNH 060800
FFGMPD
TXZ000-OKZ000-061400-

Mesoscale Precipitation Discussion 0231
NWS Weather Prediction Center College Park MD
400 AM EDT Tue May 06 2025

Areas affected...TX Big Country through Hill Country...Adj Ext
Southweset OK...

Concerning...Heavy rainfall...Flash flooding possible

Valid 060800Z - 061400Z

SUMMARY...Broad area of ascent across much of TX ahead of
anomalously deep closed low exiting the Southwest. Scattered
incidents of flash flooding possible with localized 2-3" totals
across recently saturated grounds/low FFG.=20

DISCUSSION...GOES-E WV shows core of 3-3.5 Std Dev. closed low is
finally starting to translate eastward given upstream kicker
resulting in very broad downstream diffluence/divergence area to
shift out of the High Plains into the Big Country and eastern
Edwards Plateau. A convectively reinforced shortwave is starting
to shear along the northeast quadrant of the low and pivot into E
NM still providing an axis of 700mb isentropic ascent/WAA channel
to maintain elevated convection/broadening moderate shield
precipitation across the Rolling Plains into the Big Country and
Red River Valley. Activity is scattered and generally lighter
with occasional embedded cores capable of 1"+/hr rates but
increased duration over greatest saturated soil conditions (where
precip anomalies are 300-500% of normal and remain in the upper
90th percentiles of saturation). As such, limited infiltration
will result in some enhanced run-off, but likely be limited in
coverage to those random/scattered elevated cores.

Southward into the Edwards Plateau/Hill Country...
A broad/strong axis of DPVA ahead of the main height-falls is
maintaining the 999mb low near/south of MAF, the stationary front
is starting to lift northeast as a warm front ahead of the low and
the dry line across the Western TX Panhandle is shifting eastward
increasing moisture convergence ahead of it. Warm moist winds out
of the Rio Grande Valley continue to advect 1.3-1.5" total PWats
(loaded mainly below 850mb) will continue to be highly confluent
even as they veer more southerly/southwesterly over the next few
hours. Higher unstable air with MUCAPE of 2000+ j/kg will
isentropically ascend across the front and maintain stronger thunderstorms/clusters along the boundary as they shift eastward.=20
Rates of 2"/hr are probable, though 1.5" may fall in 15-30 minutes
given 06z HRRR forecast and given some upstream cells may allow
for two rounds and/or flanking line repeating/training resulting
in spots of 2-3.5" totals mainly near/just north of the front
across the Edwards Plateau toward the Hill country. This area has
experienced less heavy rainfall than further north, so soil ratios
are much more supportive of infiltration, but the shear intense
rates have a solid probability to result in scattered incidents of
flash flooding through daybreak.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7jvy40uk_yP6qavLrS7B8BTO2TlHZvozSU9W7QSATtW51-SLaPcRVIgE48RDaXPMvNd_= 1v873evK1qD3ceg9b2Wuy_E$ for graphic product...

ATTN...WFO...EWX...FWD...LUB...MAF...OUN...SJT...

ATTN...RFC...ABRFC...WGRFC...NWC...

LAT...LON 34689941 34119755 32869680 31409681 31019684=20
30319715 29989767 29939885 30480069 30920171=20
31550195 32830212 34090165 34610071=20

=3D =3D =3D
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AWUS01 KWNH 061335
FFGMPD
TXZ000-061931-

Mesoscale Precipitation Discussion 0232
NWS Weather Prediction Center College Park MD
935 AM EDT Tue May 06 2025

Areas affected...South-Central and Eastern Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 061331Z - 061931Z

SUMMARY...Increasing thunderstorm coverage, including scattered
supercells, along a lifting warm front are expected to congeal
with thunderstorms from an eastward moving cold front to produce
locally 3"+ rainfall amounts. Flash flooding is possible with the
potential for locally considerable impacts through early this
afternoon should the heaviest rainfall occur over vulnerable urban
locations.

DISCUSSION...GOES-E WV depicts clearly a deep closed low sliding
over the southern High Plains and producing broad ascent
throughout the south-central U.S., amplified by the nose of a
110kt upper jet reaching over the Concho Valley per the 12z RAP
analysis. At the surface, a lifting warm front is evident in
recent METAR observations throughout southern and eastern TX,
between Austin and San Antonio at 12z. It is along and just north
of this boundary where the greatest potential for discrete
supercells are possible before quickly merging with an approaching
line of storms along the advancing cold front through 17z-19z.
MRMS highlights current storms of producing locally up to 2"/hr
rainfall rates, but as these storms expand, these rates will
likely cover a larger area and more likely to lead to flash
flooding impacts. However, as this line moves further into eastern
TX by midday, eastward progression will slow as flow becomes more
uniform out of the west-southwest along a stalled out boundary,
supporting back-building cells. This places areas near College
Station on eastward toward the TX-LA as having the greatest
potential for locally considerable impacts. It is this area where
the 06z HREF depicts 20-40% chances for 3"+ amounts through 18z,
with heavy rainfall likely continuing after 18z.

Recent HRRR runs highlight hourly totals of 1-4" through 19z,
which would occur within somewhat compromised terrain and where
FFG of 1-3" per 1-hr and 2-4" per 3-hr exists. This seems
reasonable given the current radar representation and environment
given the widespread 1.6-1.9" PWATs.

Snell

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_sKp8n-_lEUQ1ndcNPGAbBu9V6SjnW0wAQiPckGXesc-S7ZqaGS6YwrPty21mIlV4j7v= -C4i0rZvbrGGcT6IS6HXeTA$ for graphic product...

ATTN...WFO...EWX...FWD...HGX...SHV...SJT...

ATTN...RFC...WGRFC...NWC...

LAT...LON 32079586 31999507 31479479 30729510 29959613=20
29569780 29659907 30049937 30589896 31429763=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 061502
FFGMPD
ARZ000-TXZ000-OKZ000-062101-

Mesoscale Precipitation Discussion 0233
NWS Weather Prediction Center College Park MD
1102 AM EDT Tue May 06 2025

Areas affected...Northern Texas and Southern/Central Oklahoma

Concerning...Heavy rainfall...Flash flooding possible

Valid 061501Z - 062101Z

SUMMARY...Broad area of moderate rainfall with embedded
thunderstorms and heavier rates could lead to scattered flash
flooding with more widespread nuisance flooding through this
afternoon.

DISCUSSION...Strong ascent continues east of the closed low moving
over the southern Rockies/High Plains, while a squall line pushes
eastward across Texas. Ahead of this squall line, some scattered
supercells are possible within an elevated warm sector and MUCAPE
of 1,000-2,000 J/kg. Rainfall rates per MRMS have generally
remained below 1.5"/hr, but this area along the Red River Valley
has experienced saturated ground conditions as of late. NASA SPoRT
LIS 0-40 cm soil moisture percentiles are generally in the 70-95th
range (lower in northeast TX and southeast OK). The longer
duration of moderate to heavy rainfall (pockets of 1-2"/hr)
expected through this afternoon could lead to localized flash
flooding where terrain and ground conditions are most susceptible.
However, even where flash flooding does not occur, nuisance
flooding and ponding of water in fields/near roads is possible.

Recent HRRR runs depict 3-hrly totals up to 1.5" possible in the
highlighted MPD area, with some locations already recording
0.5-1.0" since 12z. 3-hrly FFGs in the area are less than 2.5"
from a line between DAL and OKC on westward, with eastern sections
of the MPD highlighted by 3-hrly FFGs of 3-4". PWATs over the 90th climatological percentile extend northward to the Red River, with
values over 1.7" into north-central TX ahead of the squall line.
Storms developing in this region of better moisture and strong
southern 850mb flow of 40-50kts in eastern TX will surge northward
overriding a mid-level warm front and add to the heavier mostly
stratiform rainfall through this afternoon with embedded
convection leading to the isolated flash flooding threat.

Snell

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9B6RyaImxVjtm_rl5c2NVrCOKRqLJV7RCP9EAg9HiM7eL_6loYdf1QLCvdsUxZTAN5Y9= zn6ERw2ALiY27yiVNUzEu58$ for graphic product...

ATTN...WFO...FWD...OUN...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 35749821 35669728 35289629 34679517 33979440=20
33049444 32309547 31729684 31179826 31569863=20
32439795 33399804 34689881 35379879=20

=3D =3D =3D
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AWUS01 KWNH 061626
FFGMPD
NYZ000-NJZ000-PAZ000-MDZ000-062225-

Mesoscale Precipitation Discussion 0234
NWS Weather Prediction Center College Park MD
1226 PM EDT Tue May 06 2025

Areas affected...Northern Mid-Atlantic into the Interior Northeast

Concerning...Heavy rainfall...Flash flooding possible

Valid 061625Z - 062225Z

SUMMARY...Developing convection this afternoon is expected to
repeat over areas of the Northeast and Mid-Atlantic where recent
rainfall has lowered flash flood guidance. Isolated rainfall
totals over 2 inches could lead to scattered areas of flash
flooding, with the most likely impact along the NY-PA border and
nearby areas.

DISCUSSION...A closed low over the Upper Ohio Valley continues to
churn and usher in broad southerly flow along the East Coast.
PWATs are highest along the immediate East and into New England,
where values range from 1.0-1.2" and near the 90th climatological
percentile, but the greater mix of instability and shear exists
just to the west from central New York to northern Maryland. Here,
GOES-E visible imagery depicts broken cloud cover allowing for
SBCAPE to increase over 1,000 J/kg in southeast PA, which
coincides with where the deepest convection has developed over the
last hour.

Thunderstorms are expected to continue building (although
scattered in nature) over the next few hours as instability
continues to grow and expand northward. However, a focus in
convection is possible along a weak frontal boundary/convergence
axis. All of this activity will become more widespread in
northeast PA/southern NY by about 20z once a shortwave rounding
the base of the upper trough very quickly pushes over the recent.
This increased ascent may allow for rainfall rates to approach
2"/hr and broader coverage of moderate rain, but more importantly
impact areas prone to flash flooding due to recent rainfall. NASA
SPoRT LIS 0-40 cm soil moisture is above 98th percentile for much
of northern PA and NY. This goes along with 3-hr FFG under 2"
(even as low as 1" in localized areas). The 12z HREF highlights
impressive probabilities for exceeding this FFG along the PA-NY
border just west of Binghamton by 21z this afternoon. Will
continue to monitor rainfall rates in case the need for more considerable/significant language is needed this afternoon.

Snell

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-zNr3KN6SDSE3JVMvQf89LMxtvDfaG9b8QSlF8tlYXJ27koKS-_KrG0f7Nw3b8vVNQKI= 0XNDivRwfvuLdpmKBO-7DY8$ for graphic product...

ATTN...WFO...ALY...BGM...BUF...CTP...LWX...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 43647667 43467564 42937467 41957436 40827468=20
40007534 39507640 39807705 40867721 41787734=20
42837786 43467764=20

=3D =3D =3D
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AWUS01 KWNH 061900
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-070059-

Mesoscale Precipitation Discussion 0235
NWS Weather Prediction Center College Park MD
259 PM EDT Tue May 06 2025

Areas affected...Eastern Texas and Louisiana

Concerning...Heavy rainfall...Flash flooding likely

Valid 061859Z - 070059Z

SUMMARY...Organized line of thunderstorms with hourly rates up to
3 inches expected to continue sliding eastward while additional
merging cells along a warm front increase the potential for 5 inch
totals, likely resulting in areas of flash flooding.

DISCUSSION...GOES-E CH9 WV loop this afternoon depicts a
picturesque upper low churning over the southern High Plains with
an expansive area of increased ascent extending to the east and
north, with a well-organized line of thunderstorms entering
eastern TX along a cold front. Additionally, a surface warm front
extends eastward from the squall line across southern LA, with
low-to-mid 70s dew points south of the front and 60s north. PWATs
continue to creep upward and are generally 1.7-2.0" in the
highlighted area, but will continue to rise above 2.0" across a
larger region of the central Gulf Coast per the RAP. The 06z ECWMF
highlights these values as exceeding the 99th percentile when
compared to climatology.

Rainfall totals up to 3 inches have been observed from this line
near Round Rock, TX and are expected to maintain or increase in
intensity through this evening given the increasing moisture and
daytime instability being advected northward. Helping this
northward advection is a potent 40-50kt 850mb jet extending into
eastern TX as of 18z.

Recent HRRR runs support the potential for hourly rates up to 3
inches and 5 inch totals, with the 12z HREF highlighting
widespread 20-50% chances for 3-hrly totals greater than 3 inches
in the MPD area. Although, the HRRR has been developing too much
leading convection compared to current radar data. Outside of the
eastern extent of the Texas Triangle, where 3-hrly FFGs are under
3 inches, much of LA does have elevated FFG that could inhibit the
initial impacts of heavy rainfall. However, for southern sections
of LA along the warm front, thunderstorms are anticipated to
remain less progressive and oriented more west-east (similar to
the mean wind) by this evening. Current convection near Baton
Rouge shows this potential for slow-moving warm frontal storms
that may continue and congeal with the approaching line. Scattered
flash flooding is likely within this area, with greatest potential
for significant impacts where convection is slower to progress on
the southern flank from east-central TX through central LA.

Snell

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-We7JFvC5PFF4_SXBouUY-5YNdCX72TI3auSt4vVsjxP_mBdDrWVhnm6KBf_JWkZnUsw= FXB_NfnIRJ93335YRP7QMxw$ for graphic product...

ATTN...WFO...EWX...FWD...HGX...JAN...LCH...LIX...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 33209438 33169319 32189208 31309121 30619057=20
30039088 29969184 29989302 29949431 29799642=20
30279701 31309620 32449527=20

=3D =3D =3D
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AWUS01 KWNH 062233
FFGMPD
NYZ000-NJZ000-PAZ000-070400-

Mesoscale Precipitation Discussion 0236
NWS Weather Prediction Center College Park MD
633 PM EDT Tue May 06 2025

Areas affected...central NY to PA/NJ border

Concerning...Heavy rainfall...Flash flooding possible

Valid 062230Z - 070400Z

SUMMARY...Isolated to widely scattered areas of flash flooding
will remain possible across a broad section of Upstate NY down to
the PA/NJ border through 04Z. Peak hourly rainfall up to 1.0-1.5
inches (especially early on) will be likely on an isolated basis.

DISCUSSION...Radar imagery at 2230Z showed that a broken line of showers/thunderstorms extended from near Syracuse to the NY/PA/NJ
border. A mesoscale axis of low level convergence to the west of
Syracuse has resulted in a localized area of hourly rainfall in
excess of 2 inches (north of Skaneateles) with surrounding
locations in and around central NY to northeastern PA, in the 1-2
inch range (in 60 minutes). Water vapor imagery showed a
well-defined, negatively tilted shortwave trough swinging toward
the north over eastern PA, to the east of a mid to upper-level low
center over northwestern PA. Flow ahead of this feature was
strongly diffluent, aiding in lift within a weakly unstable
airmass (500-1000 J/kg MUCAPE), though infrared cloud tops have
been warming over the past hour.

Through 04Z, the shortwave spoke is forecast to lift northward
into central NY, sending the broken convective line toward the
north and east into the Catskills and Hudson Valley. There is a
low end threat for south to north training as the line advances
east, though advection of drier and more stable air into the
region from the southwest should lessen this the heavy rain/flash
flood threat with time over eastern portions of NY.

Over central NY, weaker deeper layer mean flow will continue to be
supportive of slower movement of heavy rain cores with the ongoing
axis west of Syracuse expected to advance off toward the northeast
over the next couple of hours. Meanwhile additional heavy rain may
move in from the south through 04Z with peak rainfall rates
lowering into the 0.5 to 1.0 in/hr range as instability diminishes
with the loss of daytime heating. An additional 1-2 inches of rain
(locally a little above 2 inches over central NY) is expected on a
localized basis which may linger the flash flood threat for
another few hours over northern PA/NJ into NY.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_LvscJ0LH-UgyPdloWrQuY7y05MIaWEhDEJIGMQ_pYpb6LHRx8KqcVMcpWRivSBxpmce= GgvFt0X17xKLAfj9WEjC7ag$ for graphic product...

ATTN...WFO...ALY...BGM...BTV...BUF...CTP...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 44567573 44147450 43527391 42747368 41367401=20
41047446 41057510 41407572 41577626 41877770=20
42487817 43287778 44027718 44467636=20

=3D =3D =3D
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AWUS01 KWNH 062325
FFGMPD
AZZ000-NVZ000-CAZ000-070500-

Mesoscale Precipitation Discussion 0237
NWS Weather Prediction Center College Park MD
724 PM EDT Tue May 06 2025

Areas affected...eastern CA, southern NV, western AZ

Concerning...Heavy rainfall...Flash flooding possible

Valid 062323Z - 070500Z

SUMMARY...An increasing coverage of thunderstorms across portions
of eastern CA, southern NV and western AZ over the next 2-4 hours
will be capable of flash flooding. Rainfall of 0.25 to 0.50 inches
in 15 minutes and storm totals of 1-2 inches are expected on a
spotty basis.

DISCUSSION...GOES West water vapor imagery placed a closed
mid-level low over south-central NV at 23Z, advancing slowly to
the south. The approach of this low and its southern elongation
into CA has allowed low level winds to shift from a northerly
direction this morning to southwesterly to its south, increasing
low level theta-e values into the lower Colorado River Valley. The
combination of surface heating and low level moisture advection
has increased MLCAPE values into the 500-1000 J/kg range from
southern NV into eastern CA and western AZ via the 23Z SPC
mesoanalysis. Visible satellite and radar imagery showed a few
thunderstorms along the NV/AZ border, co-located with severe and
flash flood warnings. Visible satellite imagery also showed
developing cumulus over eastern CA with a few early thunderstorms
over the Mojave Desert.

Continued low level moisture advection into eastern CA and western
AZ is expected to allow for marginal increases in an already
highly anomalous moisture axis (standardized PW anomalies of +3 to
+4). Mean westerly deeper layer flow of roughly 10 kt from the
west will be co-located with similarly oriented and slightly
stronger 700 mb winds which will be likely to support repeating
cells and brief upwind propagation of cells. Rainfall rates within
this environment should be easily capable of producing 0.25 to
0.50 inches of rain in 15 minutes or less, which could result in
some flash flooding of low lying areas and normally dry washes.
Storm total rainfall of 1 to 2 inches is expected through 05Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_vfrOuTSTuZgQ-GHE-ivVTl3OphkUUwxyfxnNfyUUGizRv3bkOVdE4RQ_dz8I94WsHce= E2p9xS2vDy1dJ_bBFPPiV5I$ for graphic product...

ATTN...WFO...FGZ...PSR...VEF...

ATTN...RFC...CBRFC...CNRFC...NWC...

LAT...LON 36511331 36321268 35751210 35141165 34561186=20
33541272 33011382 33031480 33761571 34501618=20
35261582 35671479 36481378=20

=3D =3D =3D
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AWUS01 KWNH 070112
FFGMPD
ALZ000-MSZ000-LAZ000-ARZ000-TXZ000-070700-

Mesoscale Precipitation Discussion 0238
NWS Weather Prediction Center College Park MD
911 PM EDT Tue May 06 2025

Areas affected...southeastern TX into LA and central/southern MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 070110Z - 070700Z

SUMMARY...Areas of heavy rain will continue a significant flash
flood threat across portions of south-central LA into MS through
07Z. Hourly rainfall in excess of 3 inches will be possible along
with additional rainfall of 5 to 8 inches. These higher end
rainfall totals could result in life-threatening conditions.

DISCUSSION...Radar mosaic imagery at 0045Z depicted widespread
thunderstorm coverage from western MS into central and southern
LA, with a narrow tail of thunderstorms extending into the TX
Coastal Plain. A weakening bowing segment was observed to be
crossing into western LA with warming cloud tops over the past
hour while a persistent area of cooling cloud tops has been
observed from near JAS (far southeastern TX) to near and south of
AEX (south-central LA), co-located with the low level overrunning
via ~50 kt of 850 mb flow. The region from Newton County to
Beauregard Parish has experienced hourly rainfall in excess of 3
inches since 21Z and has MRMS-derived rainfall of 4-6 inches over
the past 3 hours ending 00Z.

As a pair of convectively induced mesoscale circulations, located
on either side of the southern AR/MS border, advance toward the
northeast within the 700-500 mb flow, the axis of strongest 850 mb
flow will slowly advance east toward the LA/MS border through 06Z.
While some weakening of the low level flow is anticipated, the
northern portion of the convective cluster should advance into MS,
while the southwestern flank will be slower to advance downstream,
being met by developing thunderstorms atop the front and
rain-cooled air over southern/southwestern LA. Training of heavy
rainfall axes will continue to be capable of hourly rainfall in
excess of 3 inches beneath a strongly diffluent flow pattern
aloft.

23Z and 00Z WoFS guidance showed a small region of 40 to 70+
percent probabilities of 5+ inches over portions of south-central
LA into southwestern MS over their 6-hr forecast range. Using the
90th percentile output as a reasonable localized high-end of
additional rainfall potential, 7 to 8 inches could fall over
portions of south-central LA into southwestern MS. These rains
could result in locally considerable to life-threatening flash
flooding through 07Z.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5KvbH6KyYdXaEI4BJ3SYIUlQ0NGVWIFaENOeKFRvjmaYcL7R2nUdfe9UObPxozDAKxkr= 7NOGiCQoCKZjKZ4GDySURV4$ for graphic product...

ATTN...WFO...BMX...HGX...JAN...LCH...LIX...MOB...SHV...

ATTN...RFC...LMRFC...SERFC...WGRFC...NWC...

LAT...LON 33678915 32628814 31348806 30648844 29938955=20
29529136 29479306 29539384 29429464 29759479=20
30529442 31439328 33139156 33569059=20

=3D =3D =3D
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AWUS01 KWNH 070644
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-071300-

Mesoscale Precipitation Discussion 0239
NWS Weather Prediction Center College Park MD
243 AM EDT Wed May 07 2025

Areas affected...Central Gulf Coast...

Concerning...Heavy rainfall...Flash flooding likely

Valid 070700Z - 071300Z

SUMMARY...Mature MCS starting to weaken with reduced inflow, but
embedded intense rates of 2"/hr will continue to over-run frontal
zone and repeat over saturating soils along I-10 maintaining
likely rapid inundation flooding concerns through daybreak.

DISCUSSION...GOES-E WV suite shows very large, anomalous closed
low over the Southern Plains with large mature MCS well displaced
at the far eastward extent of its influence. Given the broadening
of the larger cyclone, the mid to upper-level forcing is
diminishing as the jet slowly reduces in speed and responding
winds in the lower levels continue to weaken in turn. While they
are weakening, the strength and orientation remain sufficient to
maintain the complex throughout the remainder of the overnight
period with ideal split in dual jet structure with 100 kt jet
lifting northeast across NE TX into TN, while the subtropical jet
(60-70kt) ridges ideally, bending southeastward across the western
to central Gulf providing excellent divergence/evacuation for to
maintain the MCS.

The MCS's MCV is over eastern-MS but is slowly shearing along the
SW to NE flow and low level winds are veering across the central
Gulf, reducing orthogonality of LLJ to the leading squall line
across S MS into far SE LA. Source of greatest instability and
enhanced moisture also resides upstream into the northwest Gulf,
so the fast moving, but intense rain-rates will further reduce
overall totals crossing into S AL/W FL though scattered incidents
of sub-hourly 1.5-2" remain possible and urban flooding concerns
remain.

The greater concern remains upstream across western LA into
central LA, where outflow from aforementioned bow is starting to
lay flat west to east southeast LA, and perhaps align with the
slowly sagging cold front. Currently, surface to boundary layer
flow remains orthogonal to the boundary-combining front; but 850mb
flow is already veering less orthogonal out of the SW to WSW. The
jet is also expected to reduce in magnitude from 30kts toward
15kts by 10z, reducing upglide ascent. Given the Gulf remains
very warm, MLCAPEs of 2000-3000 J/kg will remain with deep moist
profile support 2-2.25" total PWats. So while flux may reduce,
the unstable environment will support scattered development from
SW LA across south-central LA with capability of 2"/hr rates.=20
Cells will once again cross saturated/flooded areas and maintain
ongoing flooding conditions through morning, with slow improvement
as scattered cells further reduce to isolated. Still pockets of
additional 3-4" totals are probable through 12z and so flooding
remains likely especially along of I-10 in LA.=20

Note: Low level flow environment is going to slack for a time
toward the end of the valid time; however, there is an upstream
shortwave that will trail the right entrance of the exiting
upper-level jet streak AoA 12z and appears to be triggering
convection west of the Lower Rio Grande Valley currently; this
will slide eastward and increase lower level flow/convergence
again with another shot of thunderstorms. Will continue to
monitor those trends closely.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6aKIpgWB3RtxG-We4i4LuB0Kxg2gwwiQMiQUe5d2tQO0QhHK3OWgvtDBrbc0wkoiDQrx= Uv4OHBbemTT4k2L6O_hSZ2o$ for graphic product...

ATTN...WFO...JAN...LCH...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...WGRFC...NWC...

LAT...LON 31948811 31928756 31708670 30978638 30348665=20
30038832 29588882 28978910 28938994 28999089=20
29179129 29399197 29629301 29699363 30019361=20
30419304 30899189 31349021 31828881=20

=3D =3D =3D
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AWUS01 KWNH 071119
FFGMPD
LAZ000-TXZ000-071505-

Mesoscale Precipitation Discussion 0240
NWS Weather Prediction Center College Park MD
719 AM EDT Wed May 07 2025

Areas affected...Middle to Upper Texas Coasts

Concerning...Heavy rainfall...Flash flooding possible

Valid 071118Z - 071505Z

SUMMARY...Repeating heavy rain along stationary front over Middle
to Upper Texas Coasts this morning. Embedded intense rates of
2"/hr will continue over the next few hours with localized
additional rain >4" and flash flooding possible immediately inland
from the coast, but south of Houston proper.

DISCUSSION...Ample Gulf moisture has surged back over the coast
along a stationary front stretching from Matagorda Bay to the
coastal border with Louisiana. Deep layer SWly flow around an
centered over western OK is parallel to a stationary front along
the coast which is limiting previous progression into the Gulf.
This analysis is not seen in recent RAP runs which depict the
front having pushed into the Gulf. So the 2" PW axis remains along
the coast where the heavy rain is occurring. This moisture,
combined with 2000 J/kg MUCAPE has allowed a line of heavy
thunderstorms to develop.

The SWly flow will allow motion in the orientation of the activity
as fresh air moves in from the Gulf allowing redevelopment. KHGX
has 1hr rainfall estimates of 1.5-2"/hr near Matagorda Bay to
southern Brazoria County. Redevelopment ahead of a multi cell
cluster just north of Matagorda Bay at 11Z, associated with a
surface low, will continue allowing repeating heavy activity and
the potential for 4" locally through about 14Z. This area has high
FFG, so any flash flooding should be limited to urbanized areas.
Since the front is quite strong, expect the heaviest activity to
remain south of Houston proper, but should a concern for the
Galveston area until the surface wave passes, shunting activity
into the Gulf.


Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8SQNAKllMapIppT-eBOrPiOtp9w_sXB27hiOCgaLyrJyX2V9ZJdnew30CgQTsPdK2ssD= myYd3bPGNVZ4FG_PPvzsSCk$ for graphic product...

ATTN...WFO...CRP...HGX...LCH...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 29829384 29679382 28949496 28489622 28909658=20
29399543 29699465=20

=3D =3D =3D
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AWUS01 KWNH 071254
FFGMPD
LAZ000-TXZ000-071805-

Mesoscale Precipitation Discussion 0241
NWS Weather Prediction Center College Park MD
853 AM EDT Wed May 07 2025

Areas affected...Southern Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 071250Z - 071805Z

SUMMARY...Continued repeating heavy rain through midday for far
southern Louisiana. The focus is pushing into the Gulf, so the
flash flood threat is considered possible, including for New
Orleans.

DISCUSSION...A stationary front remains over southern Louisiana,
though outflow is noted from regional radar as pushing into the
Gulf. There remains a heavy rain focus along the frontal boundary
south of I-10 with rainfall rates around 1.5"/hr from KLCH and
KHDC. This is despite IR GOES imagery depicting warming cloud tops
over the past couple of hours.
There is quite a PW gradient over southern LA with values of 1.75
to 1.9" south of I-10 with an east-west gradient to instability
with more over southwest LA (1500-2000 J/kg) vs southeast (around
1000 J/kg). Deep layer SWly flow around 25kt with upwind
propagation to the east will keep activity moving along the
frontal boundary to in or near New Orleans over the next few hours.
Southwest LA has been spared from the heavy rain of the past day,
so this activity is moving into less susceptible areas (though
NOLA is perpetually susceptible). The main flash flood threat
through midday is for urbanized areas.


Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8H4X-GGB03tGW4Unu-S0YcXi5ZhWcY1HXPTD2CEfoOWP21S3iY3LlgGsXTRd83nQdg8d= Qy1nNOrA21L-PtNzZEtMNWs$ for graphic product...

ATTN...WFO...LCH...LIX...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 30199118 30139021 30168943 29938900 29528952=20
29098988 28979079 29319211 29519320 29599375=20
29809393 30029345 30169261=20

=3D =3D =3D
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AWUS01 KWNH 081724
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-082322-

Mesoscale Precipitation Discussion 0242
NWS Weather Prediction Center College Park MD
122 PM EDT Thu May 08 2025

Areas affected...portions of the Lower Ohio Valley and Tennessee

Concerning...Heavy rainfall...Flash flooding possible

Valid 081722Z - 082322Z

Summary...Slow-moving showers and thunderstorms are producing
spots of 1-1.5 inch/hr rain rates at times across southern
Illinois. These rates should continue, with storms translating
slowly eastward toward central Kentucky and Middle Tennessee
through 23Z/6p CDT.

Discussion...A combination of factors was contributing to a
focused area of convective development across western areas of the
discussion area (from southern IL through northwestern TN) over
the past couple hours: 1) insolation/surface destabilization
occurring beneath a slow-moving mid/upper low over Missouri and 2)
convergence along a synoptic front extending from near SAR
east/northeast to ILN. Mid-level flow fields are relatively weak,
resulting in slow-moving and weakly organized convection that has
exhibited multiple cell mergers at times. Moisture/instability
profiles are supporting areas of 1-1.5 inch rain rates beneath the
most persistent convection and merging cells, which was resulting
in areas of FFG exceedance especially where heavier rates have
persisted for more than an hour.

Models/obs suggest that the area of convection will gradually
translate eastward mainly across Kentucky and Tennessee over the
next 6 hours or so. Occasional cell mergers/spots of FFG
exceedance are expected on an isolated basis. The combination of
both propagation and newer downstream development of convective
activity suggests that a modest increase in flash flood potential
should occur from western Kentucky eastward through the I-65
corridor, with central KY/middle TN risk peaking from 19Z onward.

Cook

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4fCaYm9r0ehHkR4D9l6qqwC_5q7d8tDwYx0CkCOgAFh7NQs0zbI5vhWrbNC0-JfsdeLx= 5L4WgRG7ZH8HeV9vbfa1kFk$ for graphic product...

ATTN...WFO...ILN...ILX...IND...JKL...LMK...LSX...MEG...OHX...
PAH...

ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC...

LAT...LON 39278510 36568497 35828675 35698910 36469000=20
37109006 37798970 38798762=20

=3D =3D =3D
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AWUS01 KWNH 082033
FFGMPD
MEZ000-MAZ000-NHZ000-RIZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-090130-

Mesoscale Precipitation Discussion 0243
NWS Weather Prediction Center College Park MD
432 PM EDT Thu May 08 2025

Areas affected...southern NY into southern/central New England

Concerning...Heavy rainfall...Flash flooding possible

Valid 082030Z - 090130Z

Summary...Isolated to widely scattered areas of flash flooding
will be possible across parts of southern NY into southern/central
New England through late evening. Hourly rainfall of 1-2 inches
with localized totals between 2 and 3 inches will be possible with
activity likely diminishing in coverage and intensity after
sunset.

Discussion...20Z visible satellite and radar imagery showed
scattered showers and thunderstorms in the vicinity of a wavy
stationary front analyzed from coastal ME into southern
NY/northern NJ. Earlier breaks in cloud cover and daytime heating
have allowed for the development of weak instability (MLCAPE up to
and locally in excess of 500 J/kg along the front over southern
New England via SPC mesoanalysis). GPS data showed PWATs were
modest, hovering near 1 inch but cell motions should be a bit
slower, somewhere between 10-20 kt from the southwest.

The coverage of showers and thunderstorms is expected to increase
within the corridor between the front and a sea breeze boundary
over southern CT into RI over the next couple of hours. The front
is also forecast by the RAP to sweep southward, west of a surface
low in east-central MA. Cell mergers, subsequent outflow and brief
training with similar cell movement and boundary orientations
could support a few spots with hourly rainfall between 1-2 inches
and perhaps storm totals between 2 and 3 inches prior to expected
dissipation after the loss of daytime heating.

The expected total rainfall is certainly on the low side, but it
may fall somewhat quickly atop a region of the Northeast which has
seen 200 to 400+ percent of average rainfall over the past 7 days,
leaving soil moisture values above average. This fact, combined
with the urban nature of the region and rush hour could result in
isolated to widely scattered instances of flash flooding over the
next 3-5 hours.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!87id6Yox9IhGQA9HdHtf3d_vLLf1C6f81DsThCFm63wkFilMFkRxMEhyLrC0EKCFEKV9= 4GX2HSU5d-3iJR46ZAZywZ8$ for graphic product...

ATTN...WFO...ALY...BGM...BOX...GYX...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 43377142 43217065 42647056 41757136 41257259=20
40927338 40577412 40657450 40757467 40967485=20
41227493 41747460 42637294=20

=3D =3D =3D
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AWUS01 KWNH 090015
FFGMPD
TXZ000-090345-

Mesoscale Precipitation Discussion 0244
NWS Weather Prediction Center College Park MD
814 PM EDT Thu May 08 2025

Areas affected...southern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 090012Z - 090345Z

SUMMARY...Localized flash flooding will be possible across
portions of southern TX with high rainfall rates of 2-3 in/hr and
isolated totals of 3-5 inches over the next 2-4 hours.

DISCUSSION...Radar imagery through 00Z showed an uptick in
thunderstorm coverage to the northwest of Corpus Christi across
the I-37 corridor where outflows were merging. Upstream, a pair of
thunderstorm clusters were advancing toward the ESE from the Rio
Grande between Eagle Pass and Laredo, co-located with an MCV-like
feature, as well as a cluster just east of I-35 near Cotulla. The
environment over southern TX was unstable with 500-2000 J/kg
MLCAPE although pockets of CIN were present near the coast from
earlier storms via SPC mesoanalysis data.

It appears probable that lift out ahead of the east-southeastward
advancing circulation/convective clusters to the west and
divergent/diffluent flow aloft, will continue to encourage
convective development downstream. Following a general ESE motion
over the next 2-4 hours will support cell mergers and occasional
slow propagation which could support high rainfall rates of 2-3
in/hr and perhaps localized totals of 3-5 inches through ~04Z over
portions of southern TX. Due to relatively high FFG values across
southern TX, any flash flooding that develops would likely be tied
to impervious surfaces tied to towns/cities within the path of the
advancing clusters of heavy rain.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6KB8RRc3fnDIWuIC2LQoVX5D0kGRB3lGvSlUEWloEYUuAae8J6BPPBS64skxZMEN9VDh= rHMH93A0OSkO0bOlOr8RvVc$ for graphic product...

ATTN...WFO...BRO...CRP...EWX...

ATTN...RFC...WGRFC...NWC...

LAT...LON 28999961 28779793 28609693 28279665 27789692=20
26899732 26859836 26909945 27399975 27860010=20
28160046 28590042=20

=3D =3D =3D
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AWUS01 KWNH 090311
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-090700-

Mesoscale Precipitation Discussion 0245
NWS Weather Prediction Center College Park MD
1110 PM EDT Thu May 08 2025

Areas affected...southwestern NC, northwestern SC and northern GA

Concerning...Heavy rainfall...Flash flooding likely

Valid 090300Z - 090700Z

Summary...Continued localized rainfall rates up to 1-2"/hr may
train and repeat over the same areas over the next several hours,
likely resulting in isolated to scattered instances of flash
flooding (with short-term totals of up to 3-5").

Discussion...Ongoing convection over the TN/NC/GA/SC border region
is tending to align in a west-to-east training axis, along an
effective low-level front (most pronounced at 1000-925 mb, per
SPC's SFCOA 02z analysis, but also apparent from 925-700 mb). This
low-level convergence is being driven by inflow/moisture transport
from the S-SW (10-20 kts from 925-850 mb), which is isentropically
ascending over rain-cooled outflow from earlier storms (and is
most apparent in the surface theta E gradient which ranges from
336K to the south to 324K to the north across the MPD).
Significant upper-level divergence is complementing the low-level
convergence, as the region is located near a phased jet structure
in the right-entrance region of a ~90 kt jet streak centered near
the Delmarva and the left-exit region of an increasingly defined,
broader jet streak spanning much of the Deep South (with the
latter becoming more of the primary influence over time).
Otherwise, the mesoscale environment is characterized by MUCAPE of
500-1000 J/kg (plenty sufficient on its own, and possibly
underselling the influence of slantwise instability via isentropic
ascent), precipitable water values of 1.1-1.4 inches (between the
75th and 90th percentile, per GSO sounding climatology), and
effective bulk shear of 30-40 kts.

While convection should have the tendency to propagate towards
towards the southeast over the course of the night (out of the MPD
area and into sandy soils beyond the fall line into the coastal
plain of SC/GA), there may be a several hour period where
convection trains from west-to-east near the aforementioned
effective front (as the upwind propagation vector, subtracting the
850 mb flow from the mean flow of the cloud bearing layer,
supports more due easterly storm motions parallel to the effective
front, as observational trends indicate backbuilding of cells over
the GA/TN/NC border region). Some of the most recent hi-res
guidance (00z ARW/ARW2 and select recent runs of both the HRRR and
experimental RRFS) indicate the potential for localized 3-5"
totals (driven by rainfall rates of up to 1-2"/hr, per both
observational trends and hi-res model data). With FLASH CREST unit
flow data already indicating localized instances of flash flooding
ongoing, expect areal coverage of flash flooding to expand over
the next several hours (with isolated to scattered instances of
flash flooding being likely, given 3-hr FFGs generally ranging
from 2.0-3.0" and the increasing likelihood of training
seagmants).

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4_Jt7mYsymeIj8vFAihyPIwAgiiRq7m7doaZpWVaYwt19kPJ-VVpS9FacR02mtsnY5oU= wUMwCuLdsP2BL2ibItKfuMU$ for graphic product...

ATTN...WFO...CAE...FFC...GSP...MRX...RAH...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 35638217 35548068 35247990 34538040 34098097=20
33728220 33988352 34338519 34818538 35098492=20
35328380=20

=3D =3D =3D
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AWUS01 KWNH 091717
FFGMPD
FLZ000-ALZ000-MSZ000-LAZ000-092215-

Mesoscale Precipitation Discussion 0246
NWS Weather Prediction Center College Park MD
116 PM EDT Fri May 09 2025

Areas affected...Southeastern Louisiana and the Central Gulf Coast

Concerning...Heavy rainfall...Flash flooding possible

Valid 091715Z - 092215Z

SUMMARY...Heavy rain threat for southeast Louisiana through the
central Gulf Coast continues through this afternoon. Convergence
of ongoing activity over southern Louisiana that should lift
northeast raises a localized flash flooding threat for vulnerable
areas including Lafayette, Baton Rouge, New Orleans, and Mobile.

DISCUSSION...A positively tilted upper trough over the Mid-South
this afternoon is providing broad scale moisture advection to the
Central Gulf Coast. A pair of surface lows over southwest and
southeast LA have slow-moving heavy thunderstorms that are
producing 2-3" in two hours per regional radar and rain gauges.
Continued low level 15-20kt southerly flow between these features,
MLCAPE of 500-1000 J/kg, and lift from the right entrance region
of an 80kt jet to the north should allow further development to
the east/north which includes the I-10 corridor and vulnerable
metro areas.
This area has seen 2-5" rainfall over the past few days with
saturated soil helping vulnerability to extend somewhat beyond the
typical vulnerable urban areas from Lafayette to Mobile. Flash
flooding is considered possible through this afternoon with
additional threats this evening as the system slowly shifts east.


Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6lgD9AHtQs1kP2SuZ2Cs0-dpGYAHCKR2GdmZrbRJczfbfRYdLoyz8GRCum46ue79gM6W= 5WckfwUznojRbEbbJe-GvPk$ for graphic product...

ATTN...WFO...JAN...LCH...LIX...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 31028791 30868695 30338721 30058826 29898918=20
29448957 29179016 29549171 29999255 30449211=20
30669095 30809024 30938888=20

=3D =3D =3D
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AWUS01 KWNH 092017
FFGMPD
FLZ000-GAZ000-ALZ000-100115-

Mesoscale Precipitation Discussion 0247
NWS Weather Prediction Center College Park MD
416 PM EDT Fri May 09 2025

Areas affected...FL Panhandle...Far Southwest GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 092015Z - 100115Z

SUMMARY...Slow-moving thunderstorms across portions of the FL
Panhandle and far southwest GA over the next several hours may
result in isolated areas of flash flooding.

DISCUSSION...The latest radar imagery continues to show several
slow-moving areas of thunderstorms across portions of the FL
Panhandle and far southwest GA. The convection has been forming
over the last couple of hours in close proximity to a frontal zone
draped across the region. A rather substantial pool of moisture
and instability is focused along this boundary with MLCAPE values
of locally near 1500 J/kg and PWs of 1.6 to 1.8 inches.

An upper-level trough upstream approaching the central Gulf Coast
will tend to favor some downstream upper-level divergence
downstream over the FL Panhandle going through the remainder of
the afternoon and into the early evening hours. This coupled with
the favorable thermodynamic environment should tend to favor
convective sustenance over the next several hours near the front
where this is also a corridor of at least modest moisture
convergence.

There will be some potential for backbuilding and training of
convective cells, and especially with some modest increase in the
low-level flow expected near the front. The presence of
smaller-scale cold pools/outflow boundaries will also tend to act
as secondary catalysts for regenerating convective cells.

Recent RRFS guidance has been tending to handle the ongoing
convective cells rather well, and suggests some localized 3 to 5
inch rainfall totals going through early this evening which will
be supported by rainfall rates of up 2 to 2.5 inches/hour.

Isolated areas of flash flooding will be possible as a result and
especially if any of these stronger storms and heavier rainfall
rates focus over the more urbanized locations.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6S39g1jTilYW1hSyyOiUBx7BDpsR9RRGNv3D8FIg2HPmTgOw-nv9hQILHvGnWGOz5qCe= koBR8IRBMK3CAtNgtzq_EIM$ for graphic product...

ATTN...WFO...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 31108480 30988355 30768312 30478315 30258435=20
30208561 30398702 30858723 31058636=20

=3D =3D =3D
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AWUS01 KWNH 100604
FFGMPD
FLZ000-ALZ000-MSZ000-101200-

Mesoscale Precipitation Discussion 0248
NWS Weather Prediction Center College Park MD
203 AM EDT Sat May 10 2025

Areas affected...portions of far southern AL/MS into the FL
Panhandle

Concerning...Heavy rainfall...Flash flooding possible

Valid 100600Z - 101200Z

Summary...Localized rainfall rates of up to 2-3"/hr may result in
short-term totals of 5"+ through 7am CDT. Isolated instances of
flash flooding are possible (and could be locally significant over
more sensitive low-lying and metro areas).

Discussion...A deep layer (surface to 500 mb) vertically tilted
cut-off low is becoming more convectively active over the past few
hours near the low-level (surface to 850 mb) center (just offshore
southeast LA and southern MS). GOES-East infrared imagery depicts
cooling cloud tops in association with this recent deep
convection, though a rainband farther east (within the core of the
warm conveyor belt) has maintained more impressive cold cloud tops
with occasional overshooting tops. Both areas of convection are
only just beginning to come ashore, though lapse rates remain
unimpressive both in the vicinity of the convection and well
onshore of both areas (max 2-6 km lapse rates of less than 7deg
C/km). That said, a corridor of increasing instability (+300-600
J/kg) is evident over the past several hours in association with
the convection near the core of the low-level center (with little
change so far in instability farther east into the FL Panhandle).
CIRA composite advected layer precipitable water (PWAT) imagery
depicts a clear increase in low-level PWAT (sfc-850 mb and 850-700
mb layers), pivoting around the center of the low-level
circulation (with both NEXRAD VWP and GOES Derived Motion Wind
Vectors (DMW) indicating 15-25 kt flow around a well-defined
surface circulation from an ideally placed ~330z ASCAT pass).
Total PWATs range from 1.7-1.9 inches (between the 90th percentile
and max moving average, per LIX sounding climatology), and
low-level moisture transport and convergence (iscentropically
ascending) is also being complemented by upper-level diffluence
(also evident in NEXRAD VWP and GOES DMW between 400-250 mb) with
deep layer (0-6 km) shear of 30-50 kts.

The latest hi-res guidance (00z HREF suite, 18z REFS suite, and
more recent runs of both the HRRR and RRFS) generally indicates
the potential for extreme localized rainfall rates (2-3"/hr) with
resulting isolated totals of 3-6"+ through 12z. The spatial
disparities in these high QPF totals are relatively wide, but have
come into better agreement (with 00z guidance onward) in depicting
the greatest potential for localized 5"+ totals in the vicinity of
the low-level center (confined to far southern portions of MS/AL,
possibly extending into the far western FL Panhandle). This is
consistent with the most recent observational trends, and 00z HREF
40-km exceedance probabilities for 5" are indicated to be as high
as 10-20% (with corresponding 100-yr ARI exceedance probabilities
of 5%). Given the high uncertainty in the manifestation of these
localized extreme rainfall rates/totals (which are largely
conditionally dependent on localized backbuilding of convection
near the low center), isolated instances of flash flooding are
considered to be possible. Given the proximity to relatively
sensitive low-lying and urbanized metropolitan areas (with 3-6
hour Flash Flood Guidance as low as 1.5-2.0"), locally significant
flash flooding is also possible.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4IwHcuJaidVMrh3-h8vB5amiBRsLWyUx5QUfof5c6c67F5wN5s7RgdhJTfIW49aXw5w5= vCEGlp7VOPbfPrbzIZT0-60$ for graphic product...

ATTN...WFO...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 31188815 31148755 31018700 30838646 30788588=20
30688535 30578502 30398468 30088453 29828468=20
29588498 29708537 30048582 30268632 30278684=20
30238745 30238749 30198859 30228915 30548913=20
30878871=20

=3D =3D =3D
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AWUS01 KWNH 101757
FFGMPD
FLZ000-GAZ000-ALZ000-102256-

Mesoscale Precipitation Discussion 0249
NWS Weather Prediction Center College Park MD
156 PM EDT Sat May 10 2025

Areas affected...Florida Panhandle into Alabama and Georgia

Concerning...Heavy rainfall...Flash flooding possible

Valid 101756Z - 102256Z

SUMMARY...Repeating thunderstorms moving north from the eastern
Florida Panhandle into Alabama and Georgia rest of this afternoon
may result in localized flash flooding.

DISCUSSION...A multi-cell thunderstorm cluster with hourly
rainfall rates of 1.5-2"/hr has developed from the eastern FL
Panhandle through far southeast AL per regional radar. This
activity expanded in the past couple of hours from an isolated
supercell in a renewed warm conveyor belt lifting from the Gulf
east of an upper low centered over southern MS. PW of 1.75" and
MLCAPE >1500 J/kg in this axis will enable further development.
Strong southerly flow from the Gulf around 35kt and a warm frontal
boundary across this axis will allow this development to continue
to be along the axis, causing repeating heavy thunderstorms and
thus a flash flood risk.

Recent HRRR runs depict a risk of 2-4" rainfall over the next few
hours. Areas in the eastern FL Panhandle received 3-5" rainfall
since last night where vulnerability is greater. Areas in
southeast AL/southwest GA have only received around an inch of
rain over the past week and are less vulnerable. Localized flash
flooding will be possible where the most repeating occurs and over
more urbanized locations.

Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6v2Of1QKyUsGiQVxQasG5djFuXW-5FiQn-JiuEL1vbyS9JUyzfIH2by-rIHK_9oApbcC= BF6AYr7kb-JLgam2nLru60w$ for graphic product...

ATTN...WFO...BMX...FFC...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32938504 32498415 31098441 29608515 30198600=20
30888589 31978595 32728564=20

=3D =3D =3D
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AWUS01 KWNH 101922
FFGMPD
ALZ000-MSZ000-110120-

Mesoscale Precipitation Discussion 0250
NWS Weather Prediction Center College Park MD
321 PM EDT Sat May 10 2025

Areas affected...Central/Eastern MS...Western /Central AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 101920Z - 110120Z

SUMMARY...Some focused areas of heavy rainfall from slow-moving
and locally training showers and thunderstorms may result in at
least isolated areas of flash flooding heading through the
afternoon and early evening hours.

DISCUSSION...The latest GOES-E visible satellite imagery shows a
fair amount of clearing across central and southern AL with strong
solar insolation ensuing. This is destabilizing the boundary layer
with the latest RAP analysis showing a nose of MLCAPE values of
500 to 1000 J/kg already nosing up around the northeast flank of
surface low pressure over eastern MS.

The greater instability is over much of southern AL, but with
additional surface heating and convergent deep layer flow
associated the slow-moving upper-level low/trough over the South,
there should be a corridor of higher instability that wraps up
across areas of central AL and into eastern MS which will be in
close proximity to a frontal occlusion.

Slow-moving bands of heavy showers and thunderstorms are expected
to evolve over the next several hours which will be supported by
divergent flow aloft around the northeast flank of the closed low
and the presence of frontal convergence and increasingly favorable thermodynamic environment.

Rainfall rates of 1 to 2 inches/hour are likely with the stronger
convective cells, and with slow cell-motions and some training
concerns, there may be some rainfall totals of 3 to 4 inches that
materialize with potential for spotty heavier amounts. This is
generally consistent with the 12Z HREF guidance which shows a 40%
to 60% chance of 6-hour rainfall totals exceeding 3 inches across
portions of west-central AL, with somewhat lower probabilities
into eastern MS.

Given the moist antecedent conditions that are in place and these
additional rainfall totals going through the early evening hours,
at least some isolated areas of flash flooding will be possible.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5bzox7HEe9SRMJoOJek5nXeEKsflhzJYE_YpTLDDpxADiviCG7Ua5ZQubEz9Bw8sSTUH= vnIHOVIqIwDOI8gkNGIXRog$ for graphic product...

ATTN...WFO...BMX...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 33908817 33668730 32918671 32118670 31848758=20
32368861 32079004 32219078 33019082 33529025=20
33848945=20

=3D =3D =3D
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AWUS01 KWNH 102221
FFGMPD
GAZ000-110420-

Mesoscale Precipitation Discussion 0251
NWS Weather Prediction Center College Park MD
620 PM EDT Sat May 10 2025

Areas affected...Central GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 102220Z - 110420Z

SUMMARY...Slow-moving supercellular MCS cluster over central GA
may result in sufficiently high enough rainfall rates for some
isolated flash flooding concerns this evening.

DISCUSSION...A long-lived supercellular MCS cluster moving
gradually through central GA continues to remain very
well-organized and has been tending to gradually track a tad to
the right over the last few hours as it begins to interact with a
warm front draped west to east across the region.

Much of the convection is aligned with a rather strong instability
gradient with as much as 1500 J/kg of MLCAPE pooled along the
front. Meanwhile, there is favorable shear in place with 0-3 km
effective bulk shear values of 30 to 40 kts which is playing a
role in maintaining the supercell character of the convective
mass. PWs across the region are quite moist with values of as much
as 1.6 to 1.7 inches and this is running a solid 1.5 to 2 standard
deviations above normal.

Rainfall rates are impressively high with dual-pol radar showing
hourly rainfall totals reaching 1.5 to 2.5 inches. The slow
cell-motions overall with this activity are yielding heavier
3-hour totals that have been on the order of 3 to 4+ inches based
on MRMS data.

Over the next few hours, the HRRR and RRFS guidance suggest a
continuation of well-organized clusters of strong convection
impacting areas of central GA with high rainfall rates that are
likely to still reach 1.5 to 2.5 inches/hour. The HRRR guidance
this evening in particular shows some back-building cells around
the southwest flanks of the convection in association with a
persistently moist southerly low-level jet of 30 to 40 kts, and
this may help drive small-scale focused areas of heavier rainfall
amounts that may reach 5+ inches.

The 18Z HREF and 12Z REFS ensemble suites both suggest at least
low-end probabilities (20% to 30%) of seeing the 3-hour FFG values
exceeded going through 03Z/11 PM EDT. Therefore, at least an
isolated threat for flash flooding is expected to exist this
evening across central GA, with the more urbanized locations at
greatest risk for impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4EXeqx2txJ9LjwExBFkX8L-ph7QLv6NombxP22FJV4jHUoQAHF591i3PpAhrj2JnJ681= kqqYG-RYeI9OQXYdnAoCeM0$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 33608236 33228194 32548200 31958269 31748353=20
31718430 32268464 33188397 33578319=20

=3D =3D =3D
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AWUS01 KWNH 111133
FFGMPD
FLZ000-GAZ000-ALZ000-111530-

Mesoscale Precipitation Discussion 0252
NWS Weather Prediction Center College Park MD
732 AM EDT Sun May 11 2025

Areas affected...Florida Panhandle into Southeast Alabama

Concerning...Heavy rainfall...Flash flooding likely

Valid 111132Z - 111530Z

SUMMARY...
Locally heavy rainfall with rates over 3 inches per hour remain
possible through the morning as training storms line up along a
stationary front. Ongoing flash flooding likely to worsen...

DISCUSSION...
A surface stationary front and a large nearly stationary upper
level low will act as the forcing mechanisms for continued deep
convection over a portion of the Florida Panhandle into
southeastern Alabama this morning. The front is drawing very moist
air with PWATs to 1.8 inches northward on a 20-30 kt SSE flow at
850. A shortwave rounding the southeastern periphery of this low
is likely further enhancing convective development as the storms
take advantage of convective instability caused by a very dry air
mass aloft overtopping the very moist air mass near the surface.

The latest HRRR runs are capturing the current convective setup
across this region fairly well, and suggest for the next 4 hours
or so that the training line of storms will continue moving almost
due north into the Florida Panhandle and continuing into
southeastern Alabama. A few other CAMs suggest that the storms may
drift east with time, but the rate of eastward movement is
uncertain and so far hasn't materialized yet...though developing
convection offshore to the east of the line may try to drift west
and merge with the storms, likely disrupting the training, even if
temporarily.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6Qx4T2Dt7eNyw0jDLWUrpjPC1bzRw5q8wkFXji2OlPVWrNpTn2jH6AYeCgC_6m20mmkp= 1bc7Pf433r1SEiqeOxPJKrM$ for graphic product...

ATTN...WFO...BMX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32018570 31928516 31858506 31598478 30698458=20
30208466 29638485 29638525 29958549 30188589=20
30368639 30378634 30738631 31198627 31858610=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 111532
FFGMPD
SCZ000-GAZ000-112131-

Mesoscale Precipitation Discussion 0253
NWS Weather Prediction Center College Park MD
1131 AM EDT Sun May 11 2025

Areas affected...Eastern Georgia into Southwestern South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 111531Z - 112131Z

SUMMARY...
A slow-moving line of training thunderstorms has developed across
eastern Georgia. Flash flooding will be possible as rainfall rates
with the strongest cores up to 3 inches per hour.

DISCUSSION... A nearly stationary line of storms has developed
across eastern Georgia in a north-south line. A moisture gradient
has set up in a pseudo dry line but in the mid levels based on 850
mb SPC mesoanalysis. On the dry side the dewpoints are as low as
6C over central Georgia, whereas on the moist side they're as high
as 13C. Thus, this is a robust gradient of moisture over the area.
The storms have formed on the moist side of that gradient, which
appear unlikely to move much over the next several hours. This
will support the potential for multiple hours of heavy rain over
the area.

HRRR and RRFS model simulations of reflectivity suggest the storms
will persist into the afternoon hours across this area, although
the behavior of individual heavy rain cores will vary through this
period. One of the biggest points of uncertainty is how the line
of convection will behave once the storms entering far southern
Georgia from the Florida Panhandle reach the latitude of the line
of storms in eastern Georgia. Assuming the mid-level dry line
weakens or dissipates as the storms tracking from Florida
approach, this should diminish the local forcing allowing the
storms to stay in place, resulting in an overall weakening of the
storms and a lessening flash flood threat. However, the RRFS
suggests that with daytime heating in full swing, that more storms
may form along the coast and result in a new training line
potentially linked to the sea breeze or the frictional gradient
along the coast resulting from the predominant onshore
southeasterly flow.

While 12Z FFGs in the area of these training storms are around 3
inches in an hour and 4 inches in 3 hours, the latter criterion
could very well be exceeded with the persistence of thses storms
over the next few hours. Flash flooding is possible.

Wegman

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_Oe3WXUCUFQaahADO9ociChMaAxsZC1GLrH26bZKgdabaOUdu7XkMBHVOf-OqpxgawPf= giZemuLia3jKuIYmtmn32nA$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...JAX...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 33888267 33868195 33528151 33078117 32518097=20
32028124 31188169 30938256 31538343 32088362=20
32448358 32968346 33448303=20

=3D =3D =3D
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AWUS01 KWNH 111932
FFGMPD
ALZ000-MSZ000-120130-

Mesoscale Precipitation Discussion 0254
NWS Weather Prediction Center College Park MD
331 PM EDT Sun May 11 2025

Areas affected...Central to Southeast MS...Central and Western AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 111930Z - 120130Z

SUMMARY...Developing bands of showers and thunderstorms will tend
to expand in coverage going through early this evening. Some
cell-training with heavy rainfall rates and also moist antecedent
conditions will favor a threat for isolated to scattered areas of
flash flooding.

DISCUSSION...The mid-afternoon GOES-E visible satellite imagery
shows a developing CU/TCU field across much of central to
southeast MS and through western AL as diurnal heating/solar
insolation work to destabilize the boundary layer in close
proximity to a frontal occlusion. In fact, LightningCast data
coupled with radar imagery does show convective initiation taking
place with a few small-scale bands of convection beginning to
organize over eastern MS and western AL

A deep layer trough/closed low continues to pivot across the lower
MS Valley, and this deep layer cyclonic flow coupled with the
improving thermodynamic environment should support developing and
expanding bands of convection going through the early evening
hours.

MLCAPE values have risen to as much as 1000 to 1500 J/kg with
3-hour CAPE differentials of 600+ J/kg and this coupled with an
expected increase in moisture convergence near the frontal
occlusion should set the stage for convection that will be capable
of producing rainfall rates of 1 to 2 inches/hour along with
concerns for cell-training given the unidirectional deep layer
cyclonic flow.

The most recent 12Z HREF guidance along with recent HRRR and RRFS
solutions support the potential for some bands of convection to
produce rainfall amounts through early this evening of 2 to 4
inches. These rains coupled with the moist and locally wet
antecedent conditions will favor a setup that may yield isolated
to scattered areas of flash flooding and especially where any
cell-training occurs.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!40BjZmTCG-9k0PUnZylJS3HLlMlPI7F1UH2yybxvcJhEmxLuuA96ZBvrUiEJdAZB7IeN= QVFwNqII89Kx2OxixplWu0A$ for graphic product...

ATTN...WFO...BMX...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34438949 33938803 32938714 32168694 31398723=20
31078770 30928820 31138885 31718922 32348971=20
33519061 34159056=20

=3D =3D =3D
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AWUS01 KWNH 112057
FFGMPD
SCZ000-GAZ000-120255-

Mesoscale Precipitation Discussion 0255
NWS Weather Prediction Center College Park MD
456 PM EDT Sun May 11 2025

Areas affected...Portions of Central and Eastern GA...SC Midlands
and Lowcountry

Concerning...Heavy rainfall...Flash flooding likely

Valid 112055Z - 120255Z

SUMMARY...Scattered areas of flash flooding will be likely going
through the early to mid-evening hours from locally slow-moving
and training showers and thunderstorms.

DISCUSSION...The latest radar and satellite imagery shows an
expansive area of heavy showers and thunderstorms impacting areas
of central/eastern GA and through western/central SC as a deep
layer southerly conveyor belt of warm and moist air lifts into the
Southeast U.S. and interacts with a stationary front draped west
to east across southern GA and the SC Lowcountry.

The deep layer moisture transport is well-defined around the
eastern flank of a deep layer trough/closed low over the lower MS Valley/western Gulf Coast region and has tropical origins with
moisture seen in CIRA-ALPW advancing north up from Central America
and the western Caribbean Sea across the eastern Gulf Coast region
and into the Southeast U.S. PW values are 1.75+ inches which are a
solid 2 to 2.5 standard deviations above normal, and the latest
850/700 mb moisture flux anomalies are as much as 2 to 4 standard
deviations above normal.

This moisture transport and warm air advection will continue to
support strong isentropic ascent across central and eastern GA and
the SC Lowcountry through this evening which combined with
moderate instability near the aforementioned front will support
areas of organized convection with heavy rainfall rates. MLCAPE
values across areas of southeast GA are still on the order of 1500
J/kg with a strongly convergent low-level flow pattern in place
given proximity of the front. However, the recent convective
activity has resulted in some lowering of CAPE values over the
last few hours.

Nevertheless, expect sufficient levels of forcing and instability
to continue going into the evening hours for additional rounds of
heavy showers and thunderstorms which will be capable of producing
rainfall rates of up to 1.5 to 2.5 inches/hour with the stronger
convective cores, and especially with the efficient/moist deep
layer tropical origins of the moisture transport.

Areas of far eastern GA and possibly getting into areas of the SC
Lowcountry will need to be closely monitored this evening for
areas of notable cell-training as the convection here should be
stronger and more focused with alignment also with the deeper
layer steering flow. A wave of low pressure traversing the
stationary front will be a key player in driving this threat.

Some additional rainfall totals may reach 3 to 5+ inches
(supported be HRRR and RRFS solutions), and given the rainfall
that has already occurred, there will likely be scattered areas of
flash flooding. This will include an urban flash flood threat,
with even major metropolitan areas well to the north including
Atlanta, GA and Columbia, SC potentially seeing some urban
flooding concerns from heavy rainfall.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-PQNebJgmP1ejftQdPTKYsNq38Pe_C5zhc11_orRsASTcEKKmm_MlpI0cl_96R4J4cha= O7Ln1hUrQxIGMPBkSrABizo$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...GSP...JAX...

ATTN...RFC...SERFC...NWC...

LAT...LON 34338150 34078036 32928007 32298059 31808105=20
31278122 31168179 32068257 32358384 33058499=20
33688492 33888415 33718258=20

=3D =3D =3D
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AWUS01 KWNH 120131
FFGMPD
TNZ000-ALZ000-MSZ000-ARZ000-120730-

Mesoscale Precipitation Discussion 0256
NWS Weather Prediction Center College Park MD
930 PM EDT Sun May 11 2025

Areas affected...Northwest to Central MS...Central and Southern AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 120130Z - 120730Z

SUMMARY...Bands of showers and thunderstorms will continue into
the overnight hours across areas of northwest to central MS along
with adjacent areas of central and southern AL. Concerns for
cell-training with heavy rainfall rates will pose a threat for
scattered areas of flash flooding.

DISCUSSION...The early evening GOES-E IR satellite imagery shows
an elongated southeast/northwest axis of relatively cold-topped
convection continuing to impact areas of central and southern AL
up across central to northwest MS. The bands of convection which
are linear in nature remain concentrated rather close to a frontal
occlusion and are persisting within a moist and moderately
unstable airmass with the aid of divergent flow aloft around the
northeast flank of the deep layer trough/closed low over the lower
MS Valley.

MLCAPE values remain locally on the order of 1000 to 1500 J/kg
with PWs of near 1.5 inches, and this coupled with some modest
shear parameters has been supporting rainfall rates of 1 to 2
inches/hour with the stronger convective cores.

There is a fair amount moisture convergence noted near the
aforementioned frontal occlusion, and this coupled with the
orientation of the convection with the deeper layer cyclonic flow
should continue to yield linear convective structures that will be
conducive for cell-training.

The latest hires model guidance led by the HRRR and the RRFS
collectively support as much as an additional 2 to 4 inches of
rain going through 06Z (1AM CDT). The additional rains are
expected to largely fall on areas that have seen recent rainfall,
and thus with moist/wet antecedent conditions in place, there will
continue to be a concern for scattered areas of flash flooding
going into the overnight hours.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_S-7MAxSPke3GGhNJFikWZviEcceWn2e7YQ5cSsQEH7acwGWDohIE35xjVUZmDtlFu86= SMupNjXu7PuUylyaeQlBq80$ for graphic product...

ATTN...WFO...BMX...JAN...MEG...MOB...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 35148972 33888795 33428640 32868585 31808589=20
31348657 31368781 31568850 31848912 32498973=20
33519061 34799086=20

=3D =3D =3D
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AWUS01 KWNH 120221
FFGMPD
SCZ000-FLZ000-GAZ000-120820-

Mesoscale Precipitation Discussion 0257
NWS Weather Prediction Center College Park MD
1020 PM EDT Sun May 11 2025

Areas affected...Central and Southeast GA...SC Midlands and
Lowcountry

Concerning...Heavy rainfall...Flash flooding possible

Valid 120220Z - 120820Z

SUMMARY...Additional rounds of heavy showers and thunderstorms
overnight will continue to promote concerns for scattered areas of
flash flooding heading into the overnight hours.

DISCUSSION...The latest radar and satellite imagery is showing new
rounds of heavy showers and thunderstorms lifting up across
northern FL and stretching up across areas central to southeast GA
and into far southern SC. This again is being supported by a deep
layer southerly conveyor belt of warm and moist air lifting into
the Southeast U.S. while interacting with a quasi-stationary
frontal zone draped across far southern GA and up across coastal
areas of SC.

The deep layer moisture transport remains well-defined around the
eastern flank of a deep layer trough/closed low over the lower MS Valley/western Gulf Coast region and continues to have tropical
origins with moisture seen in CIRA-ALPW advancing north up from
Central America and the western Caribbean Sea across the eastern
Gulf Coast/FL Peninsula and into the Southeast U.S. coastal plain.
00Z RAOB data shows PWs generally near or a little above 1.75
inches which is 2 to 2.5 standard deviations above normal.

This moisture transport and warm air advection will continue to
support strong isentropic ascent across eastern GA and the SC
Lowcountry going into the overnight hours which coupled with the
frontal convergence and pooling of instability along it will favor
additional concentrated areas of convection with heavy rainfall
rates.

MLCAPE values across coastal areas of GA and the SC Lowcountry are
on the order of 1000+ J/kg and are being aided by cyclonic
low-level flow off the warmer waters of the nearby Gulf Stream.
Favorable shear parameters are in place too, and thus the
environment will be conducive for some organized convective cells
with high rainfall rates capable of reaching 1.5 to 2.5
inches/hour.

The recent runs of the HRRR/RRFS guidance and also the 18Z
HREF/12Z REFS ensemble solutions support the potential for
additional rainfall totals reaching 3 to 5 inches. This will
support a continued threat for scattered areas of flash flooding
heading into the overnight hours.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8WF7wnE_Vld1EJtp-iCOc0LihFjsIFoY6V_v5duHBRtQTw_psBDB8h2ni18qM8AzdxFg= 052o9i4SQ4SmUHBvMcGbRzA$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...ILM...JAX...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 34348071 33827990 32817999 32108053 31468104=20
30578150 30468233 30788297 31638315 33048272=20
34058190=20

=3D =3D =3D
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AWUS01 KWNH 120734
FFGMPD
ALZ000-121100-

Mesoscale Precipitation Discussion 0258
NWS Weather Prediction Center College Park MD
333 AM EDT Mon May 12 2025

Areas affected...portions of eastern AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 120730Z - 121100Z

Summary...Continued hourly rainfall totals of up to 1-2" are
likely to result in localized 2-3" accumulations over the next
several hours. Isolated to scattered instances of flash flooding
are possible.=20

Discussion...Persistent boundary layer moisture flux convergence
just to the north of the triple point of a vertically stacked,
deep layer (sfc-200 mb) cut-off low/cyclone is maintaining a
cluster of thunderstorms across east-central AL (with MRMS
estimating localized hourly totals as high as 1-2" at times). The
convection has become increasingly linearly organized from
south-to-north within the deep layer mean flow, backbuilding
towards the triple point where 20-30 kts of low-level (primarily
near the 925 mb isobaric surface/295K isentropic surface) is
providing locally enhanced convergence/lift. In the mid- to
upper-levels (400-250 mb), broad diffluence (within the left-exit
region of a ~100 kt jet streak) and a distinct potential vorticity
max upstream should continue to promote large scale lift and
convective longevity. The mesoscale environment is characterized
by ML CAPE of 250-1000 J/kg (and increasing by ~200 J/kg over the
past several hours), precipitable water values of 1.3-1.5 inches
(between the 75th and 90th percentile, per BMX sounding
climatology), and effective bulk shear of 20-40 kts.

Given the favorable environment and recent observational trends,
the expectation is that isolated to scattered 1-2" hourly totals
will continue over the next several hours, and the potential
exists for localized training/repeating of these heavy rainfall
rates. Hi-res CAMs (recent hourly runs of the HRRR and RRFS)
insist that this activity will shift abruptly towards the
northeast over the next 2-3 hours (as the low-level flow is
expected to veer over the next couple of hours, largely cutting
off the locally enhanced moisture transport/convergence). Even so,
this will likely result in 2-3" of isolated to scattered rainfall
totals through 10-11z (falling to the north and east of the
Montgomery and Birmingham metro areas where MRMS estimates 1-2" of
rainfall has occurred over the past several hours). Antecedent
soil conditions are quite wet, with accompanying 3-hr Flash Flood
Guidance (FFGs) generally range from 1.5-2.5" (as NASA SPoRT-LIS
0-1m soil moisture remains well above the 90th percentile across
the region). Isolated to scattered instances of flash flooding are
possible.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_J_SPlRrOXtcghp3L4_NDB5gp-OB0sKIYbLllyz9vOPrylqtZzfDLiBT4AysRcBSK3X-= 4bO7GdHADcPyymcyRHtOpMI$ for graphic product...

ATTN...WFO...BMX...HUN...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34278653 34188564 33388533 32158541 32018580=20
32278604 32718625 33268647 33758657=20

=3D =3D =3D
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AWUS01 KWNH 121113
FFGMPD
FLZ000-121600-

Mesoscale Precipitation Discussion 0259
NWS Weather Prediction Center College Park MD
713 AM EDT Mon May 12 2025

Areas affected...South Florida...

Concerning...Heavy rainfall...Flash flooding possible

Valid 121115Z - 121600Z

SUMMARY...Compact MCS with rates of 2.5-3"/hr and some training
elements may result in quick 3-5" totals and rapid inundation
flooding IF collocates with urban areas over next few hours.

DISCUSSION...CIRA LPW and surface observations depict a sharpening moisture/dewpoint gradient along and southeast of Biscayne Bay,
with values in the Sfc-850mb layer near .7" while south across the
FL straits near/over 1-1.1". This is supporting an isentropic boundary/effective warm front developing due to increasing
southwest to southeast 15-25kt confluence along/ahead of NNE to
SSW convective band crossing the central Keys. This allows for an
effective triple point to exist across the Everglades along the Monroe/Miami-Dade county line. The strength of the moisture convergence/confluence and higher surface theta-E air to support
SBCAPEs of 2000-2500 J/kg will support the rapidly cooling CB tops
below -65C. Cells along the effective warm front have sufficient
bulk shear to be rotating increasing moisture flux convergence for
rainfall efficiency to greater than 2.5"/hr. Isolated, narrower
updraft cells will exist along and northeast of the triple point
through the length of the warm conveyor belt that extends north to
just east of Cape Canaveral. Cells will be less efficient within
the broader moderate shield precipitation given reduced available
instability.

There remains great uncertainty in the evolution/track of the MCV
and therefore the triple-point and warm frontal convection.=20
Dynamically biased Hi-Res CAMs (ARW, Nam-Nest, HRRR, RAP) suggest
a continued northeastward track of the MCV lifting the heavy
rainfall/triple point corridor northeastward across urban
Miami-Dade/Broward. However, thermodynamically biased guidance
(RRFS, ARW2, etc) suggest higher theta-E release in the mid-levels
and increased outflow and forward propagation out across the Gulf
stream east, resulting in a more moderate broad shield
precipitation to occur over the urban corridor. RADAR trends
would support the latter, reducing the overall risk of heaviest
rainfall to the near-offshore from Biscane Bay, eastward, but the
former cannot be fully ruled out. Currently, the greatest risk
appears to be in the Homestead/southern Dade urban areas lifting
northeast toward downtown Miami with spots of 3-5" possible over
the next 1-3 hours.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5coNZZSMvoioPfi3TcX1DHsgzScETln8Jv5VrLC5CtjPnaTzvP3qXzn2W3yJvYGn9Z3t= 76hTgMMw1GB2BWw3AbqKe7g$ for graphic product...

ATTN...WFO...KEY...MFL...

ATTN...RFC...SERFC...NWC...

LAT...LON 26918021 26707996 26068001 25638009 25218026=20
24968056 25018090 25198112 25668102 26148062=20
26768049=20

=3D =3D =3D
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AWUS01 KWNH 121927
FFGMPD
ALZ000-MSZ000-130025-

Mesoscale Precipitation Discussion 0260
NWS Weather Prediction Center College Park MD
326 PM EDT Mon May 12 2025

Areas affected...Central and Eastern MS...Western and Central AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 121925Z - 130025Z

SUMMARY...Slow-moving showers and thunderstorms this afternoon
with locally heavy rainfall rates up to 1.5 inches/hour coupled
with moist antecedent conditions will pose an isolated threat for
flash flooding.

DISCUSSION...The latest GOES-E Day Cloud Phase RGB satellite
imagery is showing the gradual expansion and continued initiation
of showers and thunderstorms across central and eastern MS and
adjacent areas of western and central AL. The convection is
largely developing underneath the deeper layer closed low
gradually pivoting eastward across the Gulf Coast states.

Cooler mid-level temperatures coupled with boundary layer heating
over the last several hours has facilitated MLCAPE values of as
much as 1000 to 1500 J/kg, and this coupled with cyclonic low to
mid-level flow should foster some increase in convective coverage
going through the remainder of the afternoon.

The environment is relatively moist with PWs generally close to
1.25 inches, but with the available instability and slow
cell-motions underneath the upper low, some hourly rainfall
amounts of up to 1.5 inches will be possible. This is consistent
with the 12Z HREF guidance which suggests some additional storm
totals by early this evening reaching as high as 2 to 4 inches
where the cells tend to locally anchor themselves.

Given the moist antecedent conditions from recent heavy rainfall,
these additional rains over the next several hours may pose an
isolated threat for flash flooding.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-9BSivFSyq4By7qv9PRu-GMcCDwbOoEOoMoiFTIsKvd-AoxrbzqhqNVMsW5NGRBOEkir= 0nTDzHp48z3FTx7oIHSU5pM$ for graphic product...

ATTN...WFO...BMX...HUN...JAN...MEG...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 34598819 34578700 34248643 33718628 33068720=20
32618952 32789082 33529100 34128995=20

=3D =3D =3D
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AWUS01 KWNH 122136
FFGMPD
FLZ000-130035-

Mesoscale Precipitation Discussion 0261
NWS Weather Prediction Center College Park MD
535 PM EDT Mon May 12 2025

Areas affected...Southeast FL

Concerning...Heavy rainfall...Flash flooding possible

Valid 122135Z - 130035Z

SUMMARY...A band of heavy showers and thunderstorms will be
approaching the urban corridor of southeast FL over the next
couple of hours. As this activity crosses the region early this
evening, and urban flash flood threat will exist.

DISCUSSION...The latest GOES-E IR satellite imagery along with
regional radar data shows a band of heavy showers and
thunderstorms gradually crossing south FL, with the activity
gradually encroaching on the I-95 urban corridor of southeast FL.

The activity has been intensifying over the last hour with cooling
convective tops noted, and this intensification trend is being
facilitated by rather strong low-level moisture convergence and a
moderate to strongly unstable airmass characterized by MLCAPE
values of 1500 to 2000 J/kg. Meanwhile, it is very moist with PWs
of 2.0 to 2.25 inches which is locally 3+ standard deviations
above normal.

Rainfall rates with the approaching convective band are expected
to be very high considering a well-defined deep tropical airmass
and robust instability. Some rainfall rates may be capable of
reaching 2 to 3 inches/hour, with even some sub-hourly rainfall
totals of as much as 1.5 inches in just 20 to 30 minutes possible.

The convection is moving fairly slowly, but steadily off to the
east, and should advance into the I-95 urban corridor of southeast
FL from West Palm Beach down to Fort Lauderdale and the Miami
metropolitan area within the next 1 to 2 hours. Given the high
rainfall rates and relatively slow cell-motions, some rainfall
totals by mid-evening could reach 3 to 4 inches.

These additional rains coupled with local sensitivities from the
rainfall that occurred this morning will pose a concern for flash
flooding over the next few hours. However, even the high rainfall
rates alone impacting the I-95 corridor of southeast FL this
evening will drive a notable urban flash flood threat.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9Xg6sWsvXY4qY09efCUo_CbCtYAexn5UKyxJaBvLrn5bZK6xj1XsxcJh_nj2TJkmxa7e= UyEhxSk_Bll6Bru4kjXiKOs$ for graphic product...

ATTN...WFO...KEY...MFL...MLB...

ATTN...RFC...SERFC...NWC...

LAT...LON 27468013 26727992 25888000 25238035 25388079=20
26308052 27428054=20

=3D =3D =3D
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AWUS01 KWNH 122349
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-130548-

Mesoscale Precipitation Discussion 0262
NWS Weather Prediction Center College Park MD
748 PM EDT Mon May 12 2025

Areas affected...Central to Northeast GA...Upstate SC...Western NC

Concerning...Heavy rainfall...Flash flooding possible

Valid 122348Z - 130548Z

SUMMARY...Scattered areas of flash flooding may materialize this
evening from areas of slow-moving and locally training showers and thunderstorms.

DISCUSSION...The early-evening GOES-E IR satellite imagery along
with regional radars shows some general increase in the coverage
of shower and thunderstorm activity across areas of central to
northeast GA which some linear structures becoming better defined
and also coinciding with some cooling convective tops.

A weakening frontal system is traversing the Southeast U.S. out
ahead of a deeper layer trough/closed low over the Gulf Coast
states, but there is a pool of moderate instability currently
situated up across areas of central to northeast GA with MLCAPE
values of 1000 to 1500 J/kg. Coinciding with this is a belt of
effective bulk shear values of 30 to 40 kts and there has been an
increase in the general organization of these cells over the last
hour.

The experimental WoFS guidance from the 20Z through 22Z runs has
been rather insistent on there being some potential this evening
for some north/south bands of convection that will be capable of
training over the same area. Recent HRRR runs have been hinting at
the same type of convective mode and potential for localized
cell-training.

Rainfall rates with the stronger storms will likely be capable of
reaching 1.5 to 2 inches/hour given their level of organization
and slow movement, and there may be some storm totals that could
locally reach 3 to 4+ inches by midnight as these storms lift
generally northward through northeast GA, portions of upstate SC,
and also eventually western NC.

Given the moist antecedent conditions and heavy rainfall potential
in the near-term, there may be some scattered areas of flash
flooding that materialize this evening.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4shPj7Yi4n01bHOoBrVwp8A_732lDSua5i-tWyoL1a4vbBnTJrO2YJaoEWKYTEr8WqK-= dcopQVf0GS94YqniOW2Np5U$ for graphic product...

ATTN...WFO...CAE...CHS...FFC...GSP...JAX...MRX...RNK...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON 36478179 36068129 34078121 32668132 31908159=20
31608216 31898263 33198284 33878289 34738292=20
35488294 36168248=20

=3D =3D =3D
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AWUS01 KWNH 131442
FFGMPD
PAZ000-MDZ000-VAZ000-WVZ000-131915-

Mesoscale Precipitation Discussion 0263
NWS Weather Prediction Center College Park MD
1041 AM EDT Tue May 13 2025

Areas affected...northern/western VA into WV/MD Panhandles

Concerning...Heavy rainfall...Flash flooding possible

Valid 131439Z - 131915Z

SUMMARY...Localized flash flooding may develop across portions of
central to western VA into the central Appalachians through 19Z.
Periods of steady rain with embedded hourly rainfall of 0.5 to 1.0
inches (locally in excess of 1 inch) can be expected with
localized 3-hr totals of 2-3 inches.

DISCUSSION...1430Z GOES East water vapor imagery showed a slow
moving closed mid-level low centered over KY/TN with a negatively
tilted shortwave spoke rotating into NC. Flow aloft ahead of this
feature was becoming increasingly diffluent over the northern
Mid-Atlantic region with a jet streak noted on GOES East DMV (~70
kt) over south-central VA. Lower level winds were oriented from SE
to NW with 850 mb wind speeds of 25-45 kt (highest from southern
Chesapeake Bay into northwestern MD), a favorable orthogonal
orientation for upslope enhancement into the axis of the Blue
Ridge and central Appalachians.

While instability was limited, central VA into east-central WV was
positioned along the gradient in RAP forecast instability with
MLCAPE of 1000+ J/kg to the southwest developing early in the
afternoon. Favorable divergence and diffluece aloft will accompany
embedded mesoscale vortices within the broader stratiform
precipitation shield, likely help to enhance rainfall rates along
with periods of short term training. Factoring in upslope
enhancement due to terrain, periods of hourly rainfall between 0.5
and 1.0 inches will be likely at times late this morning into the
afternoon with localized hourly rainfall in excess of 1 inch
possible. The steady nature of the rainfall with occasional
enhancement to rainfall intensity is expected to support 2-3
inches of rain within a 3 hour period which may result in
localized areas of flash flooding.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4uz4ytRo_taTdQ6D8wyy1zgG3jcJLAIZeZb4rZ1BEX3kW6UAcbEayJQxl5kJsIbNSGer= qzJsyssRhC034gj6sByQ0RI$ for graphic product...

ATTN...WFO...AKQ...CTP...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40437845 39777762 38197733 37357806 37467920=20
38257964 39447985 40227936=20

=3D =3D =3D
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AWUS01 KWNH 131816
FFGMPD
PAZ000-VAZ000-WVZ000-OHZ000-132245-

Mesoscale Precipitation Discussion 0264
NWS Weather Prediction Center College Park MD
216 PM EDT Tue May 13 2025

Areas affected...western VA into WV and the upper OH Valley

Concerning...Heavy rainfall...Flash flooding possible

Valid 131813Z - 132245Z

SUMMARY...Scattered thunderstorms are expected to expand from
portions of western VA into WV and adjoining areas of southeastern
OH and southwestern PA through 23Z. Hourly rates within the
afternoon storms are expected to exceed 1 in/hr at times due to
short term training.

DISCUSSION...Visible satellite and radar imagery at 18Z showed a
region of scattered thunderstorms from central WV into western VA
near I-64. These storms were located ahead of a shortwave trough
moving north from northeastern TN into western NC, part of a
larger closed mid-level low centered over KY/TN. The region was
also situated southwest of a broad region of overcast skies where
daytime heating has combined with modest moisture to support
instability. The environment near this region of thunderstorms
contained 500-1500 J/kg MLCAPE with weakly anomalous precipitable
water values with low level flow from the southeast at 10-20 kt
over western VA, but with weaker magnitudes over central WV.

The main concern for flash flooding is due to the expectation of
additional convective development ahead of the shortwave trough
within clear skies (unstable environment). While a general
movement of thunderstorms toward the north or east is expected,
unidirectional flow from the south to south-southeast will be
supportive of short-term training axis of heavy rain, capable of
generating hourly rainfall 1 to 1.5 inches (perhaps locally higher
but likely staying below 2 inches). These instances are expected
to be isolated to widely scattered but would be in excess of
hourly flash flood guidance which is near 1 inch per hour over
this region of the central Appalachians.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7Xuvk6gN6MMtXSPXK19CH4hYN-I5VIhYLOF-9Y2RSoZJcD9jWzZFCTQTVz99Ictmjf6k= D9G4Fcmweo-KYuh8W02YUYg$ for graphic product...

ATTN...WFO...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 40138083 39918020 39127989 38357957 37727941=20
37317987 37158134 37458181 38178224 38758226=20
39318201 39728164 40038123=20

=3D =3D =3D
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AWUS01 KWNH 131944
FFGMPD
PAZ000-MDZ000-VAZ000-WVZ000-140100-

Mesoscale Precipitation Discussion 0265
NWS Weather Prediction Center College Park MD
343 PM EDT Tue May 13 2025

Areas affected...South-central PA...Western MD...Eastern WV...Far
Northwest VA...

Concerning...Heavy rainfall...Flash flooding likely

Valid 131945Z - 140100Z

SUMMARY...Continued moderate rainfall with occasional weak
embedded convective elements within strong orthogonal upslope
ascent regime. Localized spots of additional 1.5-2.5" totals
possible within broader .5-1" average by early overnight.

DISCUSSION...A strong moist dynamic environment across the
Allegheny section of the larger Allegheny Plateau in far NE WV, W
MD into south-central PA is expected to persist through the
evening with a very slow south to north advancement along the
ridge lines. Highly anomalous warm conveyor belt with nearly all
CIRA LPW layers at or above the 95th percentiles with maxima at
the lowest sfc-850. Combine this with persistent, nearly
orthogonal 35-40kts of 925-700mb winds per VWP is resulting in IVT
values over 600-700 kg/m/s even without support of increased
vertical potential from insolation. As a result localized totals
have already been over 2-4" throughout the day in E WV/W MD and
starting to reach 2-3" across Somerset county in PA. Slightly
lower vertical exposure across the Blue Ridge, still spots of
1.5-2.5" have been observed. Additional rainfall will compound
and expand ongoing flooding concerns through the complex terrain
through 00z.

GOES-E WV suite shows broad closed low across the Ohio Valley,
though an eastward extension of the low/vorticity maxima is
lifting across SW VA/S WV at this time, surface winds are backing
in response to the height-falls and the 850mb trof is sharpening
increasing directional convergence from more westerly return flow
intersecting the 30-40kt WCB flow. Additionally, best diffluent
region of the upper-level jet is starting to lift northward ahead
of the 850mb trof with apex of the split along the Allegheny ridge
as noted in the broad cirrus shield (starting to evacuate Northern
VA/E WV. While there will be some insolation, the timing is
likely limited across and north of I-64; with strong instability
gradient noted in RAP analysis. Still, with the DPVA approaching
and some temps rebounding into the low to mid-70s, modified
sounding across central VA would support 500-1000 J/kg of MLCAPE
that could be utilized in further ascent on the 850mb convergence
line. Upstream convection along Albemarle/Augusta can be seen
developing in this instability axis and with 700-500mb flow veered
a bit, the cells should track NNW into the most affected areas
with localized enhancements to the WCB moisture flux to support
.5-1"/hr rates for embedded convective elements through the
complex terrain.

Rapid refresh guidance (HRRR/RRFS/WoFS) are inconsistent in
placement, as expected, but continues to support those embedded
additional 1.5-2.5" totals within a broader field of .5-1" totals,
likely to maintain on going flooding, slowly expanding coverage
northward of flooding risk through the early overnight period.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7JuH7uIBN6Hk4gtCv49xg0SFGrGWdlXSzPyAf3UafcT3ldJyuLUcVihS8kR9-UGT6qGG= pEfuEAU1HlG0B0IGqmo0Gtg$ for graphic product...

ATTN...WFO...CTP...LWX...PBZ...RLX...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 41277830 41187740 40827691 40267683 38947785=20
38107867 38167922 38757974 39667966 40617905=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 132159
FFGMPD
VAZ000-WVZ000-140300-

Mesoscale Precipitation Discussion 0266
NWS Weather Prediction Center College Park MD
558 PM EDT Tue May 13 2025

Areas affected...Western Virginia & Adj portions of Eastern WV...

Concerning...Heavy rainfall...Flash flooding likely

Valid 132200Z - 140300Z

SUMMARY...Significant flash flooding event starting to unfold
across central VA.

DISCUSSION...21z surface map depicts a highly confluent flow
strengthening a focus for very slow moving/stationary band with
training elements aligning into terrain. As noted in MPD 265, an
eastward extension of the upper-level trof continues to sharpen
across SW to S VA, supporting lee-cyclogenesis in the vicinity of
ROA to FVX. Earlier afternoon convection/moderate shield
precipitation has aided the strengthening of a surface ridge
extension through the northern Shenandoah Valley which further
helps to anchor the strengthening band of convective activity from
Nottoway to Augusta county, VA. Surface Tds in the upper 60s to
lower 70s remain located along the southwestern gradient of the
warm conveyor belt, delineated well by warm status clouds in the
1.6um near IR channel. Solid insolation across NC and southeast
VA shows a pocket of unstable air with an axis fo 2000 J/kg SBCAPE
along and south of the confluence band to maintain/focus the
convective development.

Recent Visible imagery, RADAR mosaic and lightning detection show
the strengthening/expanding nature to the entire convective line,
though the apex near the Blue Ridge continues to focus best
convergence due to the upslope. Total PWats of 1.3-1.5" and flux
at the cloud base should support rates of 1.5"/hr, increased
duration will support 1.5-3hrs of duration with slow northward
propagation and may result in localized 3-4" totals by 01z,
maintaining flash flooding conditions, where locally significant
flooding remains possible with a spot or two of 5"+ possible (in
line with recent 90th percentile for WoFS 20-21z solutions.=20

Additionally, a band of scattered storms are lifting north with
the 700-500mb trof axis across SW VA toward the area, this will
expand the risk of flash flooding southwestward within the terrain
where heavy rainfall today has sizably reduced the FFG values
below 1"/hr and 1.5"/3hr. As such, even as they pass fairly
quickly with 1-2" totals may trigger localized flash flooding
upstream, before potentially merging with the line and finally
ejecting it more northeast into more stable air near and north of
the Potomac River Valley.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!44aKQ3CFTO1oae-1CEiijb2JyLhnRDWqepZb9dSY0U689bxvzkJy87DSyFsUXdVLq7IL= KkpZWdHx4UGkz0S2VliX13o$ for graphic product...

ATTN...WFO...AKQ...LWX...RNK...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON 39047869 39037806 38587754 38067742 37607751=20
37197762 37027792 37197853 37287912 37327958=20
37477997 37887990 38347956 38717925=20

=3D =3D =3D
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AWUS01 KWNH 140317
FFGMPD
PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-140800-

Mesoscale Precipitation Discussion 0267
NWS Weather Prediction Center College Park MD
1116 PM EDT Tue May 13 2025

Areas affected...Blue Ridge Mountains across much of VA and into
MD/WV/PA, east into portions of the DMV

Concerning...Heavy rainfall...Flash flooding likely

Valid 140300Z - 140800Z

Summary...Rainfall rates of 0.5-1.0" (and locally higher) are
expected to continue over areas that have already received 2-5".
Scattered instances of flash flooding are likely to continue (with
locally significant to catastrophic impacts possible across
portions of the Blue Ridge Mountains).

Discussion...Areas of stratiform rainfall with 0.5-1.0"/hr rates
continue across much of VA and into adjacent portions of MD/WV/PA,
generally along and to the east of the Blue Ridge Mountains.
Embedded convective elements occasionally produce hourly rates in
excess of 1" (per MRMS) estimates, and this is problematically
occurring over areas that have already received 2-5" rainfall
totals over the past 12-24 hours (with some localities in the
vicinity of Shenandoah National Park receiving the bulk of that
amount over the past 3-6 hours, with multiple Flash Flood
Emergencies currently in effect). Deep cyclonic flow with a
northwestward translating mid-level vorticity max and accompanying
diffluence aloft looks to maintain synoptic scale lift and
upper-level support, while moderate to strong low-level moisture
transport (most prominent at 925 mb with 30-40 kt flow) via the
persistent warm conveyor belt directed SE-ESE across the DMV
maintains lower-level support/convergence. While instability is
beginning to wane over much of the region (-200 to -800 J/kg of
MUCAPE over the past 3 hours), buoyancy remains sufficient (MUCAPE
of 100-500 J/kg) to sustain embedded convective elements (in
addition to terrain forcing along the Blue Ridge itself).

Given the aforementioned wet antecedent conditions (with Flash
Flood Guidance over 3-6 hours generally ranging from 1.0-2.0", and
locally even below 1.0") and the expected continued rainfall rates
of 0.5-1.0" (and locally higher) over the next several hours,
scattered instances of flash flooding are likely to continue (and
may be locally significant to catastrophic).

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6C544q-j0CS5Fqexn-dky9GR_2eMLXIcVhVcs5SmIyBCwsPTFFSNAgnnqdMy6F-R8_3f= jylB6TYnng06ebUqru3UAR0$ for graphic product...

ATTN...WFO...AKQ...CTP...LWX...PBZ...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40417842 40337806 40177774 40047742 39957731=20
39827714 39677699 39417689 39037691 38777699=20
38337724 37577752 37397815 37647857 38047870=20
38597871 39387876 39557892 39707931 40027923=20
40337893=20

=3D =3D =3D
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AWUS01 KWNH 141557
FFGMPD
PAZ000-MDZ000-VAZ000-NCZ000-WVZ000-142100-

Mesoscale Precipitation Discussion 0268
NWS Weather Prediction Center College Park MD
1157 AM EDT Wed May 14 2025

Areas affected...Central Appalachians

Concerning...Heavy rainfall...Flash flooding possible

Valid 141556Z - 142100Z

Summary...Showers and thunderstorms will expand in coverage and
intensify through the afternoon across the Central Appalachians.
Rainfall rates of 1-2"/hr are expected, which could result in 2-3"
of rain in a few areas. This rain atop saturated soils could cause
instances of flash flooding.

Discussion...The GOES-E Day-Cloud distinction RGB imagery late
this morning indicates fresh updrafts beginning to expand across
northern NC and into parts of southern VA. These updrafts are
resulting in intensifying showers and isolated thunderstorms noted
via the regional radar mosaic, and are occurring in a region of
expanding lightning cast probabilities above 30%. This suggests
that destabilization is rapidly occurring, which is reflected by
the SPC RAP analysis showing that CIN has eroded and SBCAPE has
climbed to as high as 1000 J/kg. Within this environment, forcing
for ascent is increasing downstream of a potent shortwave, clearly
noted in WV imagery, lifting northward within a synoptic trough
oriented NW to SE across the region. Downstream of this trough
axis, winds veer through the column which is helping to both
transport higher moisture northward (PWs measured around 1.2
inches which is close to the 90th percentile for the date) and
force orographic lift as sfc-925mb winds lift out of the SE,
leading to an even more impressive overlap of thermodynamics and
ascent by this aftn.

The high-res CAMs are in good agreement that clusters of
thunderstorms will continue to develop and move slowly northward
on 0-6km mean winds of around 10 kts. These storms will likely
intensify through the aftn as SBCAPE reaches as high as 1500 J/kg,
which will be acted upon by the approaching shortwave and
continued orographic/upslope low-level ascent. This favorable
environment will support rainfall rates for which both the 12Z
HREF and 00Z REFS indicate have a 40%-50% probability for
exceeding 1"/hr, with the HRRR suggesting a threat for more than
0.5"/15min at times (>2"/hr rates). Although bulk shear will
remain weak at 20 kts or less, some repeating clusters of storms
are possible, lengthening the duration of heavy rain which could
lead to pockets of event-total rainfall reaching 2-3" in some
areas.

Although convection will generally remain scattered outside of
small clusters, flash flooding will be a concern beneath any heavy
rain producing cells today. This is due primarily to these
excessive rain rates moving across extremely saturated soils from
24-hr rainfall as much as 3-6". This has compromised FFG to as low
as 0.5" to 1" in 3 hours, for which the HREF and REFS both
forecast a 50-60% chance of exceedance, highest from the Blue
Ridge of VA northward into the Potomac Highlands and Allegheny
Mountains.

Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9-LiTbH9UdaoulASgam8FMpozb9ZbK3Cx0_HDNyK6MID1CASzJZmcX8shHr_UfSSPFrg= H683c8ecMNC3RWE84mKJSoA$ for graphic product...

ATTN...WFO...AKQ...CTP...LWX...PBZ...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 40277930 40047856 39297808 38207806 37227848=20
36747909 36357980 36308022 36398097 36758134=20
37578125 38808083 39778047=20

=3D =3D =3D
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AWUS01 KWNH 141734
FFGMPD
VAZ000-NCZ000-142300-

Mesoscale Precipitation Discussion 0269
NWS Weather Prediction Center College Park MD
133 PM EDT Wed May 14 2025

Areas affected...Eastern North Carolina and Virginia

Concerning...Heavy rainfall...Flash flooding possible

Valid 141733Z - 142300Z

Summary...Showers and thunderstorms will increase in coverage
through the afternoon and lift slowly northeast. Rainfall rates
may exceed 2"/hr at times within this convection, leading to
pockets of 2-3" of rain or more. This could cause flash flooding,
especially over urban areas or more sensitive soils.

Discussion...The regional radar mosaic this afternoon shows
rapidly expanding coverage of showers and isolated thunderstorms
from the Piedmont of North Carolina through the Tidewater Region
of Virginia. This convection is blossoming in response to
increased ascent through a variety of forcing including a wave of
low pressure and accompanying stationary front, the Piedmont
Trough, and a potent shortwave/vorticity maxima noted on the
GOES-E WV imagery. Together, these are producing deep layer ascent
into favorable thermodynamics characterized by PWs of 1.4-1.5
inches, around the 90th percentile at both KMHX and KWAL, with
MLCAPE measured by the SPC RAP analysis now exceeding 1500 J/kg.
At the same time, a plume of higher sfc-850mb and 850-700mb noted
in the CIRA LPW product is surging across Cape Fear, and this will
additionally enhance moisture/thermodynamics as it lifts northward
on minimally veered SW sfc-500mb flow. Rainfall rates within this
developing convection have already been estimated via KRAX and
KAKQ to exceed 1.5"/hr.

As the aftn progresses, shower and thunderstorm coverage will
likely become more widespread as reflected by available CAM
simulated reflectivity, with intensity also peaking later this
aftn and into the evening. The HREF and REFS rainfall rate
probabilities feature a 60-80% chance of exceeding 1"/hr, and
about a 20% chance of exceeding 2"/hr. Although mean 0-6km winds
should remain modestly progressive at 15-20 kts to the northeast,
Corfidi vectors collapse to around 5 kts, which when combined with
a surge of greater thermodynamics approaching from the south
suggests short term training/backbuilding is probable to enhance
the duration of these rain rates. This storm motion collapse could
also occur along the sea breeze or stationary front, providing
additional impetus for heavy rainfall accumulations, locally
exceeding 2-3" of rain.

Much of this region has been wet the past 7 days as reflected by
AHPS rainfall departures of 150-300% of normal, leading to 0-40cm
soil moisture that exceeds the 98th percentile. This has
compromised FFG to as low as 1"/1hr and 1.5"/3hrs, lowest across
southeast and south-central VA which is where HREF 3-hr FFG
exceedance probabilities are highest. Any short term training of
these intense rain rates, especially across these more sensitive
soils of VA, or atop any urban areas, could result in instances of
flash flooding into this evening.


Weiss

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5-PGRic5prtyeemOf5k_ebIL4TseZozVJycRWJMxj921jxF0khf06ifnj9WkHCaMTS5i= NozWHoq9D-QBdZVCs9nFaLo$ for graphic product...

ATTN...WFO...AKQ...MHX...RAH...RNK...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON 38067718 38007684 37817658 37347631 36787594=20
36537599 36167620 35757654 35447697 35217753=20
35107807 35427858 35677902 35877944 36027975=20
36257993 37017938 37667847 37927776=20

=3D =3D =3D
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AWUS01 KWNH 142029
FFGMPD
PAZ000-MDZ000-VAZ000-WVZ000-OHZ000-150100-

Mesoscale Precipitation Discussion 0270
NWS Weather Prediction Center College Park MD
429 PM EDT Wed May 14 2025

Areas affected...Northern WV...Southwest PA...Adj Eastern OH...
Far Western MD...Far Northwest VA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 142030Z - 150100Z

SUMMARY...Slow moving, scattered to regionally dense narrow core
convective cells capable of 1-1.5"/hr rates/totals over complex
and recently saturated soils pose localized/focused flash flooding
potential through evening.

DISCUSSION...Recent GOES-E Visible loop shows broad area of
congested cu/Tcu across northern WV into far SW PA/Garrett county
MD become more numerous and increasing in vertical depth. Area
has been confined to the north and northeast given prolonged
stratus deck limiting peak heating. Surface Tds in the upper
50s/low 60s remains well above normal and with modest mid-level
lapse rates, SBCAPEs have risen to 1500 J/kg to help
develop/maintain convective vigor for the next few hours. GOES-E
WV loop and RAP analysis denotes decaying upper-level low has
sheared from NW to SE with core of vorticity across the Piedmont
of NC/S VA with a secondary lobe back toward N OH, this has
resulted in broad northeastward lift of the trof, but also
resulted in slowing of the mid-level steering to less than
15-20kts. This should allow for strong cells to develop and
collapse within a 1-2 hour period with locally intense rain-rates
up to 1-1.5".

While localized, the overall density of the narrow cores is fairly
close in proximity, that as new development produces outflow and
seeks out remaining unstable parcels for additional development,
proximity may allow for isolated spots to have a second intense
pulse with overall spotty totals perhaps reaching 2", with highest
probability over NE WV into SW PA, as further north remains more
stable given the lack of heating this afternoon. Given these
intense rates over complex terrain naturally with lower FFG;
recent heavy rainfall in spots over the last day or so as further
reduced the capacity of soils, with increased run-off likely. As
such, scattered incidents of flash flooding are considered
possible through late evening/early overnight as instability is
exhausted.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5y3GBp-wWsDsjYStz99xzTB4Jsc7IQJSYXpbRjk44mgYA7joYS-mC4A8IyYPKSR2rl-D= _86UJu0HiFYEnBlUKUgByVg$ for graphic product...

ATTN...WFO...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40788042 40427977 39717944 39077858 37977931=20
37978049 38858081 39368114 39778148 40568117=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 142149
FFGMPD
MDZ000-VAZ000-WVZ000-150300-

Mesoscale Precipitation Discussion 0271
NWS Weather Prediction Center College Park MD
549 PM EDT Wed May 14 2025

Areas affected...Northern Virginia...

Concerning...Heavy rainfall...Flash flooding likely

Valid 142200Z - 150300Z

SUMMARY...Intense thunderstorms capable of 1.5-1.75"/hr
rates/totals within slow/chaotic cell motions regime resulting in mergers/collisions and localized 2+" totals in vicinity of
saturated ground conditions likely to induce focused/localized
incidents of flash flooding through early overnight period.

DISCUSSION...GOES-E Visible/EIR and regional RADAR mosaic show
convective evolution is a bit faster than Hi-Res CAM solutions
suggest in timing. Overall, recent HRRR solutions continue to be
consistent with other 12/18z Hi-Res CAMs with evolution of
convective activity/coverage across northern Virginia; however,
typical to slower timing bias appears to be unfolding at this time.

Strong vorticity center at southeastward end of
elongating/shearing upper-level trough from the Great Lakes/Upper
Ohio Valley is being reinforced by convective activity feeding
back into the circulation across south-central VA. A slow
north/northeastward lifting of the wave is supporting weak
cyclogenesis across central VA, as well as strengthening
northeasterly flow out of the relatively stable air out of
Maryland, further reinforcing FGEN from the surface wave near KCHO
across the western Northern Neck into the Middle Neck before
angling northward across the Delmarva. As a result, there is a
strong stability gradient along the Potomac River, making
potential for heavy rainfall reduced north of it. Weak but
sufficient low level/boundary layer southeasterly flow is
providing solid moisture of 1.5"+ north of the vorticity center
into NoVA. A few hours of solid clearing skies have resulted in
temps rising into the mid to upper 70s, resulting in increasing
SBCAPEs over 1000 J/kg toward 2000 J/kg near the tidal Potomac
River.

With the vorticity center strengthening, DPVA and modest expansion
of divergence aloft into strengthening entrance to 30-40kt 3H jet
streak over PA will continue to support upper-level evacuation for
developing convective cells/clusters. Additionally, steering flow
through 500mb will support northwest then westward motion of cells
across NoVA and with storm influences, may result in slow, chaotic
motions allowing for increased residency for any given cell.=20
While wind speeds will be relatively weak at 5-10kts for inflow,
directional convergence will aid in raising rainfall
efficiency/potential with 1.5-1.75"/hr rates possible. Given slow
motions and narrow up/downdrafts, intense cores of 2"+ totals
remain possible, especially later this evening as cells interact
with increased terrain across the Blue Ridge.

Recent significant rainfall further west toward the terrain, has
sizably reduced FFG values that even 3hr FFG values are less than
1" increasing the potential for near zero infiltration supporting
high runoff and likely flash flooding incidents. Further east
toward I-95, grounds are also have deeper wetness, with ratios in
the 60-75%, but may have more capacity that all but the highest
totals/intense rates over 1.5" may result in flash flooding. As
such, incidents of flash flooding are considered likely, but
coverage is likely to be wide spread and locally focused.=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!49AqB-LZf7dWSZCssukD0vreZbNMMatm13jez-eUS9C61rOxiPjsk87l7leOwx7UX0dz= iwfQ-TYdp4wElpvCdmRr0A0$ for graphic product...

ATTN...WFO...AKQ...LWX...

ATTN...RFC...MARFC...NWC...

LAT...LON 39577796 38977729 38777706 38217655 38007636=20
37487651 37267713 37727817 38357918 39167886=20
39567842=20

=3D =3D =3D
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AWUS01 KWNH 142355
FFGMPD
NEZ000-SDZ000-150449-

Mesoscale Precipitation Discussion 0272
NWS Weather Prediction Center College Park MD
754 PM EDT Wed May 14 2025

Areas affected...Central SDak...Northern & Central NEB Sand
Hills....

Concerning...Heavy rainfall...Flash flooding possible

Valid 142349Z - 150449Z

SUMMARY...Expanding convective cluster with very strong moisture
flux convergence, stationary downdrafts and some training elements
suggest spotty 3-4" totals in the Sand Hills and 1.5-2" totals in
Central SDak. Both may pose a few isolated to widely scattered
incidents of rapid inundation flooding.

DISCUSSION...GOES-East and West WV suite shows a pair of strong
embedded shortwave features (E ID and Northern CO/S WY) carving
out the broaden north-south synoptic trough over the northern
Rockies and northern High Plains. The pair have helped to provide
a strong deep layer convergence zone across the Dakotas generally
around 101-102W with CIRA LPW denoting pooled mid-level moisture
along and eastward with well above normal 1.25" total PWat values.
With the main shortwave exiting the WY/CO Rockies, a downstream
boundary layer to 700mb low is stacked across west-central NEB
near LBF, with a strong confluent LLJ streaming from the
southeast. This LLJ has ample anomalous low level moisture being
advected on 20-30kts with low 60s at the surface and 40-50s into
the boundary layer resulting in 1.3" total PWat, but the flux is
very strong with nearly 90 degrees of directional convergence
along the shear axis across the Sand Hills into the Dakotas.

Moderately unstable air has helped to develop convection
throughout the late afternoon/early evening across Ziebach to
Jackson county in SDak, with recent increase in vigor noted.=20
Rates of .5"/hr have steadily increased with some spots nearing
1". The concern is the deep layer steering has allowed for
training elements along it resulting in spots of 1-2" totals
starting to accumulate. Slow eastward propagation is expected but
will have to wait for a hour or two until height-falls shift the
convergence eastward. Instability will also be waning through
that time period, so there is a narrow N-S axis for these
increased totals. Localized spots of 1.5-2"+ are at the tipping
point of 1-3hr FFG values in the area, so a few localized spots
may be exceeded resulting in some flash flooding conditions in the
next 3 hours.

Further south into the Sand Hills, soil conditions can infiltrate
a higher volume of water quickly; however, the very strong
moisture flux convergence along with 1500-2000 J/kg of instability
advected will continue to support strong/broadening updrafts.=20
This has been particularly impressive in S Cherry county and has
been expanding northward and southward along a stationary front.=20
Large hail signatures have over-estimated rainfall rates, but the
amount of flux is likely supporting 1.5"+/hr rates as noted by an
observation of 1.2"/hr in Mullen, NEB. Further saturation of the
deep layer profile will further enhance rates to near 2"/hr in
spots. Strong height-falls from the ejecting shortwave are
resulting in nearly stationary cell motions as pull west is
counteracted by propagation vectors to the east-northeast. As a
result, local totals are likely nearing exceeding 2-2.5"; with an
additional 2-2.5" possible in spots. As such localized 3-4+"
totals may occur locally. FFG values suggest infiltration through
the sandy soils should take most of these totals, but the shear magnitude/volume across areas may still result in localized
flooding/ponding especially near roads/urban locations. As such,
flooding is considered possible across north-central NEB too, but
areas along/surrounding the Sand Hills will be prone for flooding
in south-central SDak before the expanding complex forward
propagates in earnest toward 03-04z.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9CUKk6Szq98yjI5KKspiJnhLapAmolslMfMretFmje_2Wax_04tEDoSSberuXxsear9h= CaXVbhW5I1jjfVJ9kSYt7sw$ for graphic product...

ATTN...WFO...ABR...FSD...LBF...UNR...

ATTN...RFC...MBRFC...NWC...

LAT...LON 45790120 44130068 43739926 43269878 42519867=20
41879904 41010090 41100215 41710251 42210192=20
42700170 43700197 44340201 45090212 45710191=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 151840
FFGMPD
VAZ000-WVZ000-160015-

Mesoscale Precipitation Discussion 0273
NWS Weather Prediction Center College Park MD
239 PM EDT Thu May 15 2025

Areas affected...eastern WV into western VA

Concerning...Heavy rainfall...Flash flooding possible

Valid 151838Z - 160015Z

Summary...Showers and thunderstorms are expected to develop over
the higher terrain of eastern WV into western VA within the next
1-3 hours. While movement of cells should be generally
progressive, exceedance of very low flash flood guidance (FFG) may
result in spotty runoff issues atop sensitive grounds.

Discussion...Visible satellite imagery at 1815Z showed an
expanding field of cumulus with increasing vertical development
over the central Appalachians of eastern WV to the Blue Ridge
Mountains of western VA. This region was located behind a
departing mid to upper-level trough over the northern Mid-Atlantic
coast within a WNW flow aloft. While the deeper moisture axis was
located over the western Atlantic, weakly anomalous precipitable
water (PW) values of approximately 1.0 to 1.3 inches remained via
area GPS PWs and a special 17Z sounding from RNK, with some
contribution to the low to mid-level layer coming from the
southwest via LPW imagery. Daytime heating has also contributed to
500 to ~1500 J/kg MLCAPE across the region via SPC mesoanalysis
data and the RNK sounding.

Continued heating of the elevated heat source(s) will likely
contribute to convective initiation within the next 1-3 hours,
based on satellite trends and short term RRFS/HRRR forecasts.
Effective bulk shear values of 35 to 45 kt combined with the
instability values should support some organized cells, capable of
higher rainfall efficiency. Individual cell motions are expected
to be fairly progressive toward the E to SE at 15-25 kt, but
potential for 0.5 to 1.0 in/hr rates will exist and considering
potential for mergers (perhaps slightly higher rates) could yield
1-2 inches through 00Z. While this is not a typical flash flood
setup for the region, conditions on the ground are hyper-sensitive
due to recent heavy rain with FFG values as low as 0.25 to 0.5
inches in an hour in some locations, with much of the outlooked
area containing FFG below 1 in/hr.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_xEb0cDxAc32sQoAaxfnSJGBjezE5lpDVI8tKOAVeiBpgA8vgwXFyTmVvb-PkhsVVzo0= iMPJZud7l4MiCgbuDBO2Kp8$ for graphic product...

ATTN...WFO...AKQ...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 39187838 38867798 37887823 37307895 37328029=20
37688069 38248069 38728009 39077944=20

=3D =3D =3D
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AWUS01 KWNH 151947
FFGMPD
NCZ000-160100-

Mesoscale Precipitation Discussion 0274
NWS Weather Prediction Center College Park MD
346 PM EDT Thu May 15 2025

Areas affected...Eastern North Carolina...

Concerning...Heavy rainfall...Flash flooding possible

Valid 151945Z - 160100Z

SUMMARY...Lingering deep moisture and slow, potentially multiple
cell/repeating tracks crossing recently saturated grounds pose
scattered incident or two of flash flooding this evening.

DISCUSSION...19z Surface and RAP analysis denotes a pool of
lingering enhanced deep layer moisture across eastern NC that has
had near full isolation throughout the day resulting in quite
unstable environment. Sfc Tds in the low 70s with low to upper
80s extending from the VA/NC line south to a few 90s near
Lumberton, NC; and modest 7 to 7.5C/km lapse rates have resulted
in a pool of MLCAPE over 3000 J/kg across the area of concern.=20=20
Surface analysis shows a broad surface trof from upstate NC toward
a weak low near DAN/GSO with the Fall-line trough extending
southward through central SC; stronger winds from SC at 10-15kts
slow in proximity to the temperature gradient increasing flux
convergence.=20

GOES-E Visible loop shows enhanced convergence lines with the
sea-breeze, but overall general congestus across central NC is
starting to bubble to a few TCu/CBs near RAH. Deep layer
850-700mb southwesterly flow will veer a bit more with slightly
confluent streamlines across the state in proximity to the surface
trof and low. Isolated cells will build to be scattered through
the evening, but given updraft strength and flux capability of TPW
AoA 1.5", should support 1.5-1.75"/hr rates. Cell motions of
10-15kts will help with duration and may support some spots of
enhanced rainfall. As cells become more clustered toward the east
into the late evening (potentially locked to terrain due to
bay/sea-breeze boundaries), there are increased chances of
localized 2-3" totals.=20

Normally, soils would support these rates, but given recent
400-600% of normal rainfall across portions of E NC per AHPS, and
soil saturation ratios above the 98th percentile in the range of
65-80% (greater along and east of I-95), FFG values may have
rebounded a bit too quickly but 3hr FFG value of 2.5-3" are still
in range of some exceedance, the risk of limited infiltration and
rapid inundation flooding is considered possible.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!98_8g15ot8znuugGKkTQ43XlbPTbDGOIuR9S-WWaffEBDew1o3gxBCr0w36eg2ubVN88= z54NxlJ5vkwB9IuFJRu14MQ$ for graphic product...

ATTN...WFO...AKQ...MHX...RAH...

ATTN...RFC...SERFC...NWC...

LAT...LON 36547686 36407611 35967578 35637586 35177663=20
34867736 34897829 35077906 35397933 35867943=20
36387884 36517783=20

=3D =3D =3D
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AWUS01 KWNH 161137
FFGMPD
TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-161630-

Mesoscale Precipitation Discussion 0275
NWS Weather Prediction Center College Park MD
737 AM EDT Fri May 16 2025

Areas affected...Northeast Arkansas through Central Kentucky

Concerning...Heavy rainfall...Flash flooding possible

Valid 161134Z - 161630Z

Summary...Repeating heavy thunderstorms continue developing from
northeast Arkansas through central Kentucky this morning. While
movement of cells remains progressive, cell mergers and repeating
activity makes flash flooding possible.

Discussion...Numerous supercells have developed ahead of a
stationary front over northeast Arkansas, the Missouri Bootheel
and western Kentucky. Gulf-sourced moisture (PW of 1.8") is
pooling along the front with higher instability (MUCAPE >2000
J/kg) and powerful deep layer WSWly flow (60kt) allowing for heavy
repeating cells. Rainfall up around 1.5" in the past hour as been
estimated from the heaviest cells which have large hail. The 09Z
RRFS is decent with its current depiction with a diurnal increase
in coverage through the rest of the morning. Flow parallel to the
front will allow repeating storms.

Flash flood guidance is 1.5 to 2" per hour, so flash flooding
should be limited to where repeating heavy activity occurs.


Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_1tfTVs699s6-4k1XkAri7sZh3oy2tit-HTTPl7u9WuYCx97jRqUIb4InJAemZ043UsC= ao5rsCLZN5J1gYraksY2HTA$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...LZK...MEG...OHX...PAH...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38448437 37168364 36478611 35728928 35169145=20
35639212 36189161 36758983 37338844 38108616=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 161407
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-161905-

Mesoscale Precipitation Discussion 0276
NWS Weather Prediction Center College Park MD
1007 AM EDT Fri May 16 2025

Areas affected...Southeast Pennsylvania Through New Jersey

Concerning...Heavy rainfall...Flash flooding possible

Valid 161406Z - 161905Z

Summary...Organized thunderstorms progress to the northern
Mid-Atlantic coast through the early afternoon. 1.5"/hr rainfall
rates could cause localized flash flooding, particularly over
urban areas such as Philadelphia and Wilmington, DE.

Discussion...Mesoscale convective system (MCS) progressing over
Pennsylvania will continue to move ESE over a low amplitude trough
extending up the Eastern Seaboard. Gulf-sourced moisture, with PW
of 1.5" (2 sigma over normal) spreading up from the Southeast is
riding over a warm front extending from southern PA through the
Delaware Bay. Instability is sufficient (around 1000 J/kg) along
the frontal boundary with a notable decrease below 500 J/kg over
central New Jersey which is directly downstream of the activity.
However, upscale growth is seen in IR imagery with continued
cooling in the core of the system over east-central PA.

Hourly CAMs (HRRR and RRFS) have struggled with intensity and
timing of this system. However, given the sensitivity of the large
urbanized areas downstream of the MCS and history of leading cells
adding to rainfall impacts, there is a localized flash flood risk
through mid-afternoon.

Additional risk for heavy rain in the Mid-Atlantic later this
afternoon and evening will continue to be monitored.

Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-Ih3aHS-OCGz35h_OQuVdxf-bCcH3P9x1surIhyxWpeJQ6xG4Z-xYmJiRuLzQp6UhlY5= sDKXFRXK-2ASt0bRuc0AxSo$ for graphic product...

ATTN...WFO...BGM...CTP...OKX...PHI...

ATTN...RFC...MARFC...NWC...

LAT...LON 41027647 40697470 40247370 39357414 39157460=20
39487556 40097709 40627752=20

=3D =3D =3D
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AWUS01 KWNH 161524
FFGMPD
VAZ000-NCZ000-WVZ000-OHZ000-TNZ000-KYZ000-162015-

Mesoscale Precipitation Discussion 0277
NWS Weather Prediction Center College Park MD
1123 AM EDT Fri May 16 2025

Areas affected...South-Central Appalachians

Concerning...Heavy rainfall...Flash flooding possible

Valid 161519Z - 162015Z

Summary...Risk of repeating heavy thunderstorms across the
south-central Appalachians this afternoon. Fast motion to these
storms will continue, so flash flooding is possible where cell
mergers and repeating of the heaviest activity occurs.

Discussion...Numerous supercells embedded in a quasi-linear system
east of a stationary front will continue to develop and shift east
over the south-central Appalachians this afternoon. Gulf-sourced
moisture (PW of 1.7 to 1.9") is pooling ahead of the front with
higher instability MLCAPE 1500 to 2500 J/kg) and powerful deep
layer WSWly flow (50 to 60kt) allowing for heavy repeating cells.
Peak hourly rainfall estimates of 1.0 to 1.5" per hour continue in
the heaviest cells which also have hail present. The RRFS
continues to have a decent handle on this regional activity
especially compared to recent HRRRs which are too late with
activity. The 13Z RRFS indicates potential for 3" over the next
few hours which is reasonable given the repeating threat from flow
parallel to the front.

Flash flood guidance decreases east from KY with terrain with
three-hour values of 1.5 to 2" decreasing to as low as 1". Given
the axis of higher instability continuing through the crest of the Appalachians, there is a notable threat for flash flooding in
spite of the fast cell motion.


Jackson

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5n6lhpSV2aOGa-JlZUmxQ7UBI471RTs10LVLX_K2zJ5YPlFuQiUx-7HMOcOsVTfixl0w= p86S_Hbs6HlCrxD5CLx0IFo$ for graphic product...

ATTN...WFO...JKL...LMK...LWX...MRX...OHX...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 38588107 38537968 37937903 37107891 36287983=20
36208569 37638499 38308328=20

=3D =3D =3D
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AWUS01 KWNH 161752
FFGMPD
MEZ000-NHZ000-170000-

Mesoscale Precipitation Discussion 0278
NWS Weather Prediction Center College Park MD
152 PM EDT Fri May 16 2025

Areas affected...Northern NH...North & Northwest ME...

Concerning...Heavy rainfall...Flash flooding possible

Valid 161800Z - 170000Z

SUMMARY...Widely scattered but very slow moving thunderstorms with
capability of 1.5"/hr and focused spots of 2-3" are possible,
resulting in possible localized flash flooding.

DISCUSSION...Well before arrival of eastern edge of very
broad/deep layered cyclone across the Great Lakes, a surge of
enhanced moisture sourced from the tropics/sub-tropics a week or
so ago lifted northward across northern New England and has
lingered in place. Total moisture values of 1.25-1.3", mainly
loaded from the surface to 700mb as noted by upper 50s low 60s
Tds, and 850-700mb CIRA LPW within the 95th-99th percentile (for
the running mean over the last 20 years). Combined with solid
clear skies and ample insolation throughout the day ahead of forcing/approaching cirrus deck, CAPEs have risen to 1000-1500
J/kg across the area of concern.=20=20

VWP and RAP analysis shows recent switch of boundary layer (850mb
winds) to the south with values increasing to 15kts. Given weak
capping, this has been sufficient convergence in proximity to
higher terrain/upslope to break out isolated to widely scattered
convection over the last few hours from the Presidental Range
through the northern deep woods of Maine with a few cells reaching
-45 to -50C. GOES-E WV suite shows vorticity center at mid-level
intersection of weak warm conveyor belt lifting northeast but will
be also peeling more northward over the next few hours this will
bring some weak favorable upper-level divergence ascent pattern to
help maintain convection but also result in further expansion of
the 500-1000mb thickness ridge. With mean steering flow being
weak at 5-10kts, this further helps to reduce forward propagation
vectors, with some hints in Hi-Res CAMs that retrograding cells
may occur toward the north and northwest with the approaching
height-falls. This should support longer localized duration and
with increasing convective coverage, higher potential for cell
interaction and mergers. Given mild moisture flux and
instability rates of 1.25-1.5" are possible. As such, localized
widely scattered incidents of 2-3"+ may occur especially with any mergers/repeating through the late afternoon.

While the area is remote/low population, it is fairly rugged and
FFG values (minus the localized maxima near/north of Laconia, NH)
of 1-1.5"/hr & 1.5-2" are well within range of being exceeded
within/near the cores of these cells, and as such an incident or
two of localized flash flooding is considered possible through
00z.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Oi-V1B6cMaJw-S1ygvQDOCiF6RGiwOu8jcPzcGVUN2Jlti_30umJ-1MzUz1dPxzsj0I= hNeb1gjzgj9x6xfUhlBTh2U$ for graphic product...

ATTN...WFO...CAR...GYX...

ATTN...RFC...NERFC...NWC...

LAT...LON 47496897 47196785 46306773 45596830 44856964=20
43667092 43857186 44997123 45997052 47216964=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 162204
FFGMPD
KYZ000-INZ000-ILZ000-170330-

Mesoscale Precipitation Discussion 0279
NWS Weather Prediction Center College Park MD
604 PM EDT Fri May 16 2025

Areas affected...Much of Kentucky...Adj Southern IL/IND...

Concerning...Heavy rainfall...Flash flooding possible

Valid 162200Z - 170330Z

SUMMARY...Individual cells likely to expand and become more
linearly oriented, tracking through areas already saturated.=20
Additional 2-3" totals (in 1-3hrs) over the 1-3" from this
morning, may result in scattered incidents of flash flooding into
early overnight period.

DISCUSSION...Initial cluster of super-cells is tracking through S
IL entering western KY at this time, with additional development
along the unstable areas surrounding them. Further expansion of
the cluster is expected over the next few hours as cells continue
to march through broad nose of 30-40kt southwesterly LLJ.=20
Environment across western and central KY has nicely rebounded
with temperatures into the mid 80s over upper 60s/low 70s Tds,
while insolation was limited as dense high-CB anvils obscure the
ground, instability has built back to well sufficient levels to
maintain strong buoyancy through the late evening/early overnight
period as cells rapidly race eastward. Strong moisture flux into
the broad super-celll updrafts have increased rainfall efficiency
over the last few hours with quick 1-1.5" sub-hourly totals
estimated and some .75-1" totals noted upstream in SE MO.=20

Initial convection will continue to expand and feed along the
eastern edge of the LLJ with 1.5" total PWats feeding in, but
overall the LLJ will narrow and veer ever so slightly, to become a
bit more oblique to the outflow boundaries and allow for
isentropic ascent/convergence along the flanking lines. Deep
layer steering, while very strong and mean winds over 60kts, will
slowly orient a bit more parallel to the updrafts supporting some
short-term training of the flanking cells. 18z HRRR 15-minute
rain totals occasionally reach 1.25-1.5" with the line as it
progresses and as such spots of 2-3" are expected (generally
aligning with 20-21z WoFS 50th to 90th percentile totals). Slow
southward propagation will expose much of western and central KY
to this additional heavy rainfall. This is of greater concern
given the 1-3" totals that fell this morning. NASA SPoRT 0-40cm
soil ratios got as high as 80-85% and FFG values reduced to less
than 1.5"/hr across much of the area of concern with spots below
.75"/hr into the more rugged terrain of central to eastern KY.=20

Additionally, secondary development is probable along the cold
front that has lagged the initial development with some continued
heating and return moisture/instability flux through the MS River
Valley. Additional upstream development, may further aid
scattered repeating, further exacerbating any flooding conditions.
So all considered, while severe weather is primary threat,
especially across the next few hours; heavy rainfall will present
sufficient totals to result in possible scattered incidents of
flash flooding as well.

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5FQSdt0kihQS_ChSagzFC57PMrZtSy4bQ9EHiIDINbgDX2_qtt-38mQgYH1igcKLCvj0= 5YULwxTj5m_CQcy9xxXLsi4$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...PAH...RLX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38728491 38528337 37868269 37288308 37048399=20
36878565 36758699 36678874 37108912 37648864=20
38148754 38538625=20

=3D =3D =3D
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AWUS01 KWNH 170112
FFGMPD
TNZ000-KYZ000-MOZ000-ARZ000-170415-

Mesoscale Precipitation Discussion 0280
NWS Weather Prediction Center College Park MD
912 PM EDT Fri May 16 2025

Areas affected...Northeast AR...Northwest/Northern Middle
TN...Bootheel of MO...

Concerning...Heavy rainfall...Flash flooding possible

Valid 170110Z - 170415Z

SUMMARY...Upstream redevelopment and flattening steering flow
support training environment for increasingly efficient rainfall
producing thunderstorms.

DISCUSSION...Regional RADAR and GOES-E 10.3um EIR loop shows line
of severe/enhanced V overshooting top signatures continue to
back-build along/ahead of the slowly advancing cold front across
SE MO into NW AR. Strong speed shear aloft shows narrow wedge but
fairly undirectional steering flow, generally parallel to the
developing line along the front. Surface inflow of low to mid 70s
Tds on 15-20kts of flow, veers to 45kts out of the WSW at 850mb,
increasing moisture flux convergence to the updrafts. The deeper
aligning LLJ is also increasing overall moisture values from 1.5
toward 1.7/1.8" in total PWat values. As such, rainfall
efficiency is increasing with rates currently reaching 1.5"/hr but
will start climbing toward 2"/hr. Combine this with short-term
training profiles and localized totals of 2-4" are becoming
increasingly possible, especially as mature cells to the north
increase cold pool geneation and propagate more south of due east
into the path of these upstream developers.

Cells are along the south and southwest edge of areas that
received heavier rainfall this morning and FFGs reflect this
ranging to aroudn 1.5"/hr and 2-2.5"/3hrs. Further south of the
area of concern where recent drier conditions have existed, FFG
values are about a 'category' higher at 2-2.5"/hr and
2.5-3.5"/3hrs.=20=20

Gallina

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-MvhQmWbvnKieiVcTNm4NLzjOA9PrXTJ_nS_2j2MXN0W3qKV5mkp4mwadYxqCVnrbkaw= --iQqcc9E-pv1_H6kokxe6U$ for graphic product...

ATTN...WFO...LZK...MEG...OHX...PAH...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 36658931 36618829 36608773 36568530 36118555=20
35548893 35299096 35639184 36249136 36609015=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 170316
FFGMPD
VAZ000-WVZ000-OHZ000-TNZ000-KYZ000-MOZ000-ARZ000-170915-

Mesoscale Precipitation Discussion 0281
NWS Weather Prediction Center College Park MD
1115 PM EDT Fri May 16 2025

Areas affected...Portions of the OH/TN Valleys

Concerning...Heavy rainfall...Flash flooding possible

Valid 170315Z - 170915Z

SUMMARY...Strong to severe thunderstorms will continue into the
overnight hours across portions of the OH/TN Valleys, and will be
capable of also producing heavy rainfall totals. A combination of
cell-mergers and cell-training with moist antecedent conditions
will maintain a threat for scattered areas of flash flooding.

DISCUSSION...A well-organized severe weather outbreak continues to
unfold across areas of southern OH down through especially central
to southwest KY and northwest TN as a deep layer closed low
advances east across the upper Midwest and sends a cold front
southeastward into a very moist and unstable airmass.

MLCAPE values this evening remain locally quite high across
especially central KY through western TN with values of 2000 to
3000 J/kg in place. This strong instability continues to work in
tandem with enhanced shear profiles with 50 to 70+ kts of
effective bulk shear to support supercell convection with an
evolution into multiple linear bands/QLCS of activity over the
next several hours as the broader convective threat advances
eastward.

The onset of nocturnal cooling will be initiating a gradual
stabilization of the boundary layer and thus introducing some
low-level CINH, but the hires model guidance suggests some
intensification of the southwest low-level jet to as much as 50+
kts by 06Z. This should maintain a strong degree of moisture and
instability transport up across especially central and northern TN
through central and eastern KY that will be conducive for
maintaining a corridor of well-organized convection with heavy
rainfall rates.

Rainfall rates with the stronger and more organized cells will be
capable of reaching 2 inches/hour, and with some likelihood for
seeing cell-merger activity and cell-training, some additional
rainfall totals of 2 to 4 inches will be possible. This is
consistent with the 00Z HREF guidance, and it should be noted that
recent HRRR runs overall appear to be locally a bit underdone with
its QPF potential considering the high rainfall rates and
cell-training concerns.

The antecedent conditions across much of the region are quite
moist, and some areas saw heavy rainfall just within the last 12
to 18 hours. As a result, the additional rainfall amounts may
result in scattered areas of flash flooding overnight.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6PWZMbL2SI6-aVebvdYnKT9Bm1kg1Wi4pF_DChZcHM7ZcaMU4nlY3I25chwg2XN5i0H4= _WPFeVs7jaH2vQ9BxK1ri8o$ for graphic product...

ATTN...WFO...ILN...JKL...LMK...MEG...MRX...OHX...PAH...PBZ...
RLX...RNK...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 39848076 38698000 37528106 36408303 35738505=20
35418803 35718965 36508976 37168760 37818589=20
38548465 39618286=20

=3D =3D =3D
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AWUS01 KWNH 171638
FFGMPD
NHZ000-VTZ000-NYZ000-172230-

Mesoscale Precipitation Discussion 0282
NWS Weather Prediction Center College Park MD
1238 PM EDT Sat May 17 2025

Areas affected...northeastern NY into VT/NH

Concerning...Heavy rainfall...Flash flooding possible

Valid 171636Z - 172230Z

SUMMARY...Localized to widely scattered instances of flash
flooding will be possible from northeastern NY into north-central
New England through early evening. While the majority of cells are
expected to be progressive, cell alignment will occasionally favor
areas of short term training, capable of producing 1-2 inches of
rain in an hour or less.

DISCUSSION...16Z visible satellite and radar imagery showed
scattered thunderstorms from eastern Lake Ontario into the
Adirondacks, in the wake of a preceding swath of
showers/thunderstorms advancing through VT. The storms over
northeastern NY were located just downstream of the leading edge
of a mid-upper level closed low centered over Lake Huron, within
the diffluent left exit region of a 90-110 kt upper level speed
max located just south of the closed low. The environment over
northeastern NY into VT contained 500-1000 J/kg MLCAPE and 1.1 to
1.4 inches of precipitable water per 16Z SPC mesoanalysis data.

Daytime heating in the wake of overcast skies departing toward the
east from VT (and eventually parts of NH) should allow for an
expansion of CAPE across the region with 500-1500 J/kg likely from
eastern NY into central/north-central New England over the next
2-4 hours. Forecast stalling of a warm front over southern NH
should limit the northeastward extent of instability and therefore
rainfall intensity over eastern NH at least through late
afternoon. A mixture of storm types will be possible given
sufficient shear and instability but individual cells are expected
to average 25-35 kt from the southwest. The concern for flash
flooding will come from multiple rounds of cells over the same
location and/or brief alignment of cells with the mean wind to
support short term training. These scenarios could allow for 1-2
inches of rain in an hour, or even as short as 15-30 minutes,
given the strong ascent ahead of the upper low. 1-2 inches of rain
(perhaps localized 3 inch totals) will be capable of localized to
widely scattered flash flooding through 22Z. However, the coverage
of these higher rainfall totals should stay somewhat limited
across the region.

Otto

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-7EM3pHbT7goWxmX10YGl1NPzHOPV8cGSEUpYB-UnBbR_Yct8s7eVOu09P55KJnodLJs= jsL5Un_9piRR3fgAOEN0WF4$ for graphic product...

ATTN...WFO...ALY...BGM...BTV...BUF...GYX...

ATTN...RFC...NERFC...NWC...

LAT...LON 45217212 44987141 44247144 43467192 42777243=20
42747308 42967348 43157380 43177476 43227535=20
43217581 43417609 43667612 43967584 44407513=20
45057386=20

=3D =3D =3D
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AWUS01 KWNH 180515
FFGMPD
MSZ000-ARZ000-180913-

Mesoscale Precipitation Discussion 0283
NWS Weather Prediction Center College Park MD
114 AM EDT Sun May 18 2025

Areas affected...Portions of Central AR

Concerning...Heavy rainfall...Flash flooding possible

Valid 180513Z - 180913Z

SUMMARY...Some clusters of locally repeating/training showers and
thunderstorms south of Little Rock and into the Pine Bluff
vicinity may continue for a few more hours and result in a
continuation of at least an isolated urban flash flood threat.

DISCUSSION...The latest GOES-E IR satellite imagery along with
regional radar shows a couple of clusters of cold-topped
convection impacting areas of central AR. There is evidence of a
modest MCV traversing the region which is interacting with the
proximity of stationary front and a moist/unstable airmass pooled
along it.

Despite the increase in boundary layer CINH associated with
nocturnal cooling, there remains as much as 2000 to 3000 J/kg of
MUCAPE which coupled with a modest southerly low-level jet of 20
to 30 kts overrunning the front continues to help favor some
active convection across the region.

The southwest flank of the overall MCS has been characterized by
some cooling convective tops over the last couple of hours as this moist/unstable airmass continues to lift into the region in an
elevated fashion. Over the next few hours, the convection will be
capable of locally repeating/training over the same location, with
areas south of Little Rock and especially near the Pine Bluff area
seeing the greatest threat of this.

Rainfall rates with the stronger storms will be capable of
reaching 1.5 to 2.5 inches/hour, and some isolated additional
totals of 3 to 4 inches will be possible. A localized urban flash
flood threat will exist as a result.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5EGZlEQIqtiQPOA4W2rDRvnMOVaF0TkyXnOxmOS7c5IlSLNl5ZJmc0IRe_6pjlmaNd27= USnMxNDbEoa3YtoeZdsVhcg$ for graphic product...

ATTN...WFO...JAN...LZK...MEG...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 34649207 34419083 33939089 33779169 33959293=20
34249333 34569308=20

=3D =3D =3D
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AWUS01 KWNH 182150
FFGMPD
TXZ000-OKZ000-190300-

Mesoscale Precipitation Discussion 0284
NWS Weather Prediction Center College Park MD
549 PM EDT Sun May 18 2025

Areas affected...Northwest and North TX into far southern OK an

Concerning...Heavy rainfall...Flash flooding possible

Valid 182150Z - 190300Z

Summary...Rapidly growing thunderstorms near a bulge in the
dryline may result in rainfall rates as high as 2-3"/hr (and
short-term totals of 3-5" with localized backbuilding). Isolated
to scattered instances of flash flooding are possible.

Discussion...Thunderstorms are rapidly initiating late this
afternoon along a bulge in the dryline in the vicinity of Abilene,
TX, near a maximum in surface-based instability (with 21z RAP
analysis indicating 3000-5000 J/kg of SBCAPE across the greater
North TX region). Convection should rapidly grow upscale in this
mesoscale environment, which is also characterized by precipitable
water values of 1.5-1.9 inches (between the 90th percentile and
max moving average, per FWD sounding climatology), and (equally
anomolous) deep layer shear of 50-60 kts. GOES-East water vapor
imagery suggests a subtle shortwave trough near Midland, TX may be
contributing to enhanced lift, and an associated ~100 kt jet
streak (embedded within the broader phased jet structure) may also
be ideally situated to the north (providing enhanced upper
divergence via the right-entrance region). Storm mode may
initially favor splitting supercells (relatively straight
hodographs) with bunkers right vectors favoring much slower ENE
motion (~25 kts) relative to the mean wind (~45 kts). With
rainfall rates as high as 2-3"/hr anticipated, any backbuilding
and training could result in significant short-term (3-6 hour)
localized totals. This is expected to drive the greatest localized
flash flood threat to the west of the DFW metro area (though
upscale development into an MCS may allow for upwind propagation
towards the ESE, and backbuilding along the western flank could
bring training of heavier totals farther east into the DFW metro
area).

Hi-res CAMs are in relatively good agreement with regard to
convective initiation along the (very well modeled) bulge in the
dryline, though resulting QPF does vary quite dramatically. Some
of the stronger solutions suggest the potential for 3-5" totals
(mainly the FV3 and RRFS, the later of which has outlier solutions
of 5"+ with some of the hourly runs). Taking a more probabilistic
approach with the HREF and RRFSe ensemble systems (18z and 12z
runs, respectively), a 40-km neighborhood method suggests a chance
(15-30%) of 3" exceedance and a slight chance (10-20%) of 5"
exceedance. These probability maxima are mostly concentrated to
the north and west of the DFW metro areas, but an upwind
propagating MCS could bring the threat of these totals into the
DFW metro (and surroudning) area as well. Isolated to scattered
instances of flash flooding are possible (and could be locally
significant should backbuilding of convection manifest).

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Xx0ler_E1yqiuvG2mxWyG8iBYDFiP8mCnHnL_bZRSp2KrYpMX8Nl4JGsNYNnXOUUIBU= HMescxKkMwd_B6P1O_on_j0$ for graphic product...

ATTN...WFO...FWD...OUN...SHV...SJT...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34319646 33889576 32839560 31459626 31109773=20
31270024 32290012 33869946 34309805=20

=3D =3D =3D
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AWUS01 KWNH 190223
FFGMPD
MOZ000-IAZ000-KSZ000-NEZ000-190600-

Mesoscale Precipitation Discussion 0285
NWS Weather Prediction Center College Park MD
1023 PM EDT Sun May 18 2025

Areas affected...Central to Southeast NE...North-Central to
Northeast KS

Concerning...Heavy rainfall...Flash flooding possible

Valid 190220Z - 190600Z

SUMMARY... Scattered to numerous clusters of strong to severe
thunderstorms will pose an increasing threat for isolated to
scattered areas of flash flooding over the next few hours.

DISCUSSION...The mid-evening GOES-E IR satellite imagery shows
scattered to numerous areas of heavy showers and thunderstorms
impacting much of central to southeast NE and into north-central
to northeast KS. Very cold cloud tops are associated with the
activity and there continues to be an array of supercell activity
embedded within the larger scale convective envelope across the
central Plains region.

Ejecting height falls associated with a deep layer trough over the
central Rockies will continue to advance gradually east over the
Plains which will encourage the persistence of a strong south to
southeast low-level jet of 40 to 60 kts over the region going into
the overnight period. The low-level jet is overrunning a
well-defined frontal zone and is yielding strong moisture and
instability transport with a corridor of enhanced isentropic
ascent poleward of the front.

MUCAPE values across southern NE through eastern KS in close
proximity to the front are as high as 1500 to 2500 J/kg and with
strong effective bulk shear values of 50+ kts favoring
well-organized clusters of convection. This setup should continue
over the next few hours going through at least 06Z (1AM CDT), and
with the enhanced moisture transport and convergence near the
front, there will an environment conducive for additional
cell-mergers and some cell-training.

Rainfall rates are expected to locally reach 2.5 to 2.5
inches/hour, with some additional storm totals of 3 to 4+ inches
going through 06Z (1AM CDT). While antecedent conditions across
the region are generally dry, the arrival of heavy convective
rainfall along with the localized persistence of it over the next
few hours will support a concern for isolated to scattered areas
of flash flooding. The more urbanized locations in particular will
be more sensitive to this threat.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9nCF6knr4PxQF8kVSnqwbBA6k5lLXCeNU12CoNUtdIfivBZ8YTx7mWeMWKhzYsYLaeU1= TpGnvn9WruDpSqPaxazBXVI$ for graphic product...

ATTN...WFO...EAX...GID...LBF...OAX...TOP...

ATTN...RFC...ABRFC...MBRFC...NWC...

LAT...LON 42179992 41909763 41139609 39839494 38909459=20
38629512 38799628 39969918 40820108 41770129=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 190451
FFGMPD
MOZ000-KSZ000-191030-

Mesoscale Precipitation Discussion 0286
NWS Weather Prediction Center College Park MD
1250 AM EDT Mon May 19 2025

Areas affected...Far Southeast KS...Southwest MO

Concerning...Heavy rainfall...Flash flooding possible

Valid 190450Z - 191030Z

SUMMARY...Showers and thunderstorms may become a bit more
concentrated over the next few hours over areas of far southeast
KS and into southwest MO. Heavy rainfall rates and locally
repeating cell-activity may result in sufficient rainfall totals
for scattered areas of flash flooding overnight.

DISCUSSION...Strong warm air advection with enhanced low-level
moisture transport along with proximity of a strong elevated
instability gradient is expected to set the stage for heavy shower
and thunderstorm activity becoming a bit more concentrated over
the next few hours across areas of far southeast KS and into
southwest MO. This is all focusing well ahead of a deep layer
trough edging out into the central Plains as a warm front
gradually lifts northward across the region.

A sharp instability gradient is noted in a northwest to southeast
fashion across eastern KS down through far southwest MO and into
northwest AR where this front is located, and there is as much as
1500 to 2500 J/kg of MUCAPE along the boundary. This coupled with
strong shear profiles and the nose of a 30 to 40+ kt southerly
low-level jet has been yielding increasingly concentrated areas of
heavy showers and thunderstorms over the last couple of hours.

Given some additional nocturnal enhancement in the low-level jet
overnight, this convection may attain some greater coverage and
organization with MCS development/evolution possible near the warm
front. The convection should tend to advance off to the east with
time, with some east-southeast motion possible along the
instability gradient if convection grows upscale into an MCS
overnight.

The 00Z hires model CAMs are generally in terrible agreement with
respect to the convective details overnight, but recent GOES-E IR
satellite imagery is showing cooling cloud tops over especially
far southeast KS, and this trend favor an expansion of convection
into southwest MO in at least the near-term.

Rainfall rates with the stronger storms may reach 1.5 to 2
inches/hour, and some localized storm totals by dawn may reach 3
to 4 inches. This will be supported by a conducive environment for
some repeating cell-activity near the aforementioned warm front.
Some scattered areas of flash flooding will be possible where
these heavier rainfall totals set up.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8Klv7UJElzFeOvudX46NcuY9Q_C-iJETPVuQLB-z7mQZSKEy4T3PMasWHLNiEpSw8Qw6= 3QBQOLqLxxgnK4qKwc1lgl8$ for graphic product...

ATTN...WFO...EAX...ICT...LSX...SGF...TOP...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 38719375 38439254 37839180 37339162 36739194=20
36759328 37219449 37629502 38229513 38609459=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 190542
FFGMPD
TNZ000-ALZ000-MSZ000-190940-

Mesoscale Precipitation Discussion 0287
NWS Weather Prediction Center College Park MD
140 AM EDT Mon May 19 2025

Areas affected...Northern MS and Northern AL

Concerning...Heavy rainfall...Flash flooding possible

Valid 190540Z - 190940Z

SUMMARY...A locally training band of showers and thunderstorms
with high rainfall rates will continue to impact portions of
northern MS while gradually moving east into downstream areas of
northern AL over the next 2 to 3 hours.

DISCUSISON...The latest radar imagery shows a broken band of heavy
showers and thunderstorms traversing portions of northern MS
(especially north of Tupelo) with an alignment north of a
quasi-stationary front. This convection which is effectively a
small-scale MCS has been rather long-lived at this point and
continues to move east along a well-defined instability gradient
pooled along the front.

There continues to be as much as 1500 to 2000 J/kg of MLCAPE over
areas of northeast MS through northern AL, and the convective mass
will likely tend to be sustainable for at least a few more hours
given favorable low-level moisture convergence nosing in along the
southwest flank of the convection where warm air advcetion is more
pronounced. Additionally, there is proximity of at least a weak
MCV near the MS/TN border which should favor at least some modest
mid-level forcing.

Rainfall rates with this MCS have had a history of being quite
high and upwards of 1.5 to 2.5 inches/hour. Over the next 2 to 3
hours, the RRFS which has the best handle on this system (albeit a
tad too far north), suggests an eastward extension of heavy
convective rains that would allow for northern AL to be impacted.

Some of these areas in general across northern MS and northern AL
are quite moist from recent rainfall, and the arrival of as much
as another 2 to 3+ inches of rain may allow for some runoff
concerns and at least an isolated threat for flash flooding.

This will especially be the case over northern AL where there is
some locally higher/sloped terrain and thus potential for more
efficient runoff given the high rainfall rates. Areas that will
likely be impacted over the next 2 to 3 hours will include Muscle
Shoals and eventually the Huntsville vicinity.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6RHvC0rpznoIBbk7DBnOZeZT79lcZCMUj_ebjgFNtpBftmrY9X_oU-BE89KIKfhXI_xR= SoNrjNxPcDM1s9NeWZ8ze0Q$ for graphic product...

ATTN...WFO...BMX...HUN...MEG...OHX...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 35068805 35068653 34918569 34388579 34158810=20
34258924 34488983 34848987 35038910=20

=3D =3D =3D
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AWUS01 KWNH 190631
FFGMPD
MOZ000-IAZ000-NEZ000-191030-

Mesoscale Precipitation Discussion 0288
NWS Weather Prediction Center College Park MD
231 AM EDT Mon May 19 2025

Areas affected...Southeast NE

Concerning...Heavy rainfall...Flash flooding possible

Valid 190630Z - 191030Z

SUMMARY... Heavy showers and thunderstorms will continue to impact
areas of southeast NE for a few more hours which will maintain a
threat of isolated to scattered areas of flash flooding. The more
urbanized locations will be at greatest for any impacts.

DISCUSSION...GOES-E IR satellite imagery along with the regional
radar mosaic shows an expansive clustering of heavy showers and
thunderstorms over southeast NE which continues to be driven by a
strong warm air advection pattern downstream of an upper-level
trough ejecting out across the central Plains.

Enhanced moisture and instability transport with aid from a south
to southeast low-level jet of 40 to 60 kts continues to surge over
a warm front. MUCAPE values 1000 to 2000 J/kg remain in place, and
the strong isentropic ascent/frontogenetical forcing on the
poleward side of the warm front will help to maintain the
organized elevated convective threat for at least a few more hours.

Rainfall rates will continue in the near-term to be as high as 1.5
to 2 inches/hour, and there will still be a threat for some
localized small-scale linear bands of convection that train over
the same area. This may yield some additional spotty rainfall
amounts of 2 to 4 inches.

The additional rains over the next few hours will maintain a
threat for isolated to scattered areas of flash flooding with much
of this concern focus around the more urbanized locations.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8ppNkW8ARl_FcmcBoGMLPKuYGoe24tSiO4PH51muFFbIH1CPv4olLvINsQAlp77Hk011= diXE4_fCbtUhVaMqaE_Bb7M$ for graphic product...

ATTN...WFO...EAX...GID...OAX...

ATTN...RFC...MBRFC...NWC...

LAT...LON 41899722 41709633 41139555 40349543 40109603=20
40089698 40299815 40719873 41329870 41799814=20 =20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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AWUS01 KWNH 192048
FFGMPD
MOZ000-IAZ000-KSZ000-200047-

Mesoscale Precipitation Discussion 0289
NWS Weather Prediction Center College Park MD
447 PM EDT Mon May 19 2025

Areas affected...eastern KS into northwest MO and far southern
central IA

Concerning...Heavy rainfall...Flash flooding likely

Valid 192047Z - 200047Z

Summary...Continued 1-2" hourly totals likely to train over the
same areas, resulting in short-term (3-4 hour) rainfall totals of
3-5". Scattered instances of flash flooding are likely.

Discussion...Clusters of thunderstorms have rapidly developed and
organized across eastern KS into northwest MO this afternoon,
within an area of strong warm air advection (along a warm front
and extending well into the warm sector of an associated cyclone).
The mesoscale environment is characterized by MUCAPE of 2000-3000
J/kg, PWATs of 1.4-1.8 inches (between the 90th percentile and
daily max record, per TOP sounding climatology), and (equally
anomolous) deep layer (0-6 km) shear of 50-60 kts. Storms are fast
moving in this environment (generally following the 850-300 mb
flow of 40-50 kts towards the NNE), but the tendency to orient
parallel to the mean flow is resulting in highly efficient hourly
rainfall totals of 1-2" (per MRMS estimates). Continued training
of these efficient cells is likely, resulting in localized
short-term (3-4 hour) totals of 3-5" (and supported by 12z HREF
40-km neighborhood probabilities of 20-40% for 3-hr 3" exceedance
through 00z). Scattered instances of flash flooding are likely.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9-PWbF8AIbhXy1oPXeNrpK2OygwWLLIYv-Z-iyZsEdpk9Rjo2ge80LkEhNtfDrHHD7yD= buhpGbSgtmAsbLoeS1EFGNE$ for graphic product...

ATTN...WFO...DMX...EAX...ICT...SGF...TOP...

ATTN...RFC...ABRFC...MBRFC...NWC...

LAT...LON 40809422 40649294 38399355 37369473 37629577=20
38789555 40049494=20

=3D =3D =3D
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AWUS01 KWNH 192157
FFGMPD
MOZ000-ARZ000-TXZ000-OKZ000-KSZ000-200200-

Mesoscale Precipitation Discussion 0290
NWS Weather Prediction Center College Park MD
556 PM EDT Mon May 19 2025

Areas affected...far North TX into much of central and eastern OK,
adjacent portions of far northwest AR, southwest MO, southeast KS

Concerning...Heavy rainfall...Flash flooding likely

Valid 192155Z - 200200Z

Summary...Hourly rainfall as high as 2-3" to result in additional
localized 3-6" through 02z (9pm CDT). Scattered instances of flash
flooding are likely (and may be locally significant).

Discussion...Discrete clusters of supercells are gradually
becoming more prolific across far North TX into much of central
and eastern OK, within a mesoscale environment characterized by
SBCAPE of 2500-5000 J/kg, PWATs of 1.6-2.0 inches (near or
exceeding the daily max value, per OUN/SGF sounding climatology),
and deep layer (0-6 km) shear of 55-65 kts (above the 90th
percentile). While storm motions are generally fast in this
environment (with both the deep layer mean flow and bunkers right
vectors 45-55 kts towards the NNE-NE), storms are increasingly
organizing linearly with localized training of cells already
resulting in some 2-3" totals (with MRMS and some local
observations starting to indicate these totals in as little as an
hour). As convection continues to organize with the approach of a
potent shortwave trough over the TX Panhandle, expect convection
to continue to proliferate and grow upscale with already
substantial divergence aloft only further increasing (as the MPD
region is within a very favorable placement between semi-phased
subtropical and polar jet streaks). This may eventually result in
somewhat slower (20-30 kt) storm motions more generally towards
the east as convection begins to propagate upwind (towards the
low-level jet, per the Corfidi vectors).

Until convection organizes more linearly with meaningful eastward
propagation, expect storms to continue to increase in coverage and
result in additional localized training elements with additional
localized totals as high as 3-6" possible (per hourly HRRR and
experimental RRFS output, which has corrected westward in recent
runs relative to the 12z HREF and 00z RRFS suites). Experimental
WoFS 90th percentile of accumulated rainfall also agrees with this
potential (and even indicates the potential for isolated 6"+
totals north of the DFW metro area in far North TX with
backbuilding towards the dryline with unimpeded strong low-level
inflow from the Gulf). Scattered instances of flash flooding are
likely (and may be locally significant, especially if 6"+ totals
occur over sensitive localities that have seen as much as 2-3" of
rain over the past 3-24 hours).

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!59xDXd0SdSLI66eX_ARHnkHbV6RnZ4_HBJT9Y53aSEJp8Rhvy0pI1S--IA_0HcA9d4--= JCfcn5uqDK4XuhpkzzUzA7Y$ for graphic product...

ATTN...WFO...FWD...ICT...LZK...OUN...SGF...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 37279552 36909358 35889340 34449471 33559584=20
32919792 33419840 35279669 36669617=20

=3D =3D =3D
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AWUS01 KWNH 200045
FFGMPD
MOZ000-IAZ000-KSZ000-NEZ000-200430-

Mesoscale Precipitation Discussion 0291
NWS Weather Prediction Center College Park MD
844 PM EDT Mon May 19 2025

Areas affected...northeast KS, northwest MO, south-central IA, and
far southeast NE

Concerning...Heavy rainfall...Flash flooding likely

Valid 200040Z - 200430Z

Summary...Continued thunderstorms (up to 1-2"/hr rates) within the
warm sector of a nearby low pressure system will likely result in
additional localized 2-4" totals through 0430z (1130 PM CDT).
Scattered to numerous instances of flash flooding are likely (and
may locally be significant in the vicinity of the Kansas City
metro area).

Discussion...Thunderstorms are once again expanding in coverage
once again across portions of eastern KS, this time a bit farther
west closer to the dryline (which is in the process of being
overtaken by a lagging cold front). While much of the earlier
convection has progressed north and east since the prior MPD,
rainfall totals over the past 4 hours have been locally as high as
1.5-5.0" (with the highest totals near and immediately north and
northeast of the KC metro, where MRMS FLASH CREST unit streamflow
indicating ongoing minor to moderate flooding, which has been
gradually subsiding). Despite the earlier convection, the
mesoscale environment remains supportive of heavy rainfall, with
MLCAPE of 500-2500 J/kg, PWATs of 1.3-1.7 inches (above the 90th
percentile, per TOP sounding climatology), and highly anomalous
deep layer (0-6 km) shear of 50-60 kts. The recent convection
along the dryline has been much slower to advance with localized
backbuilding, but should start to propagate upwind (towards the
ENE-E at 20-30 kts) as cold pools becoming more established (and
eventually by the synoptic forcing of the cold front).=20

The expectation is for localized 1-2"/hr rates to continue in this
favorable environment, given observational trends and recent
hi-res model data. This convection is likely to pass over the same
areas that have recently received heavy rainfall, and may even
locally train/repeat as well (as the mean 850-300 mb flow remains
parallel to the dryline and ongoing convection). This should
result in additional localized totals of 2-4" (as indicated
consistently by runs of the HRRR since 20z, as well as the 50th
percentile of accumulated rainfall from the experimental WoFS).
Given 3-hr Flash Flood Guidance (FFG) of 2.0-3.0" (which largely
doesn't take into account the recent rainfall), scattered to
numerous instances of flash flooding are likely.

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9vU_1Bw_WMlQLx0iMhaVTtrRKejjusIpoBJ-iLLr8HAXIAkd_EasNV5PsQqt3g_G_hgM= ZaES5oTOrL7-2gSiWQ9L-TY$ for graphic product...

ATTN...WFO...DMX...EAX...ICT...OAX...TOP...

ATTN...RFC...ABRFC...MBRFC...NCRFC...NWC...

LAT...LON 41779594 41729509 41499419 40829308 40249281=20
39219325 38399442 37769665 38329694 39449642=20
40339680 40939678 41549652=20

=3D =3D =3D
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AWUS01 KWNH 200203
FFGMPD
MOZ000-ARZ000-TXZ000-OKZ000-200600-

Mesoscale Precipitation Discussion 0292
NWS Weather Prediction Center College Park MD
1002 PM EDT Mon May 19 2025

Areas affected...southeast OK, northwest and central AR, adjacent
portions of far North TX

Concerning...Heavy rainfall...Flash flooding likely

Valid 200200Z - 200600Z

Summary...Linear convective system to continue producing hourly
1-3" rainfall, additional localized 3-hr totals as high as 3-5"
(through 05z, midnight CDT). Scattered to numerous instances of
flash flooding are likely to continue, and may locally
significant/life threatening.

Discussion...Thunderstorms have undergone significant linear
organization across portions of the Southern Plains, now moving
gradually into the Lower MS Valley as the QLCS (quasi-linear
convective system) propagates upwind to the E-ESE. The system has
a history of producing very heavy rainfall (hourly rainfall as
high as 2-3" with training/repeating segments), and some overlap
with already hard hit areas is possible along the southwest flank
(as has been consistently depicted by the experimental WoFS, still
indicating the potential for hourly 2-3" totals near the Red River
of the South). The mesoscale environment along and ahead of the
convective system is characterized by MLCAPE of 1750-3500 J/kg
(highest along and out ahead of the southwest flank), PWATs of
1.7-2.0 inches (near the daily max moving average and record daily
levels, per FWD and LZK sounding climatology), and tremendous deep
layer (0-6 km) shear of 55-65 kts. Strong low-level moisture
transport is being appropriately offset by divergence aloft
(evident via GOES-East water vapor imagery, as the area remains
ideally wedged between a semi-phased jet stream with subtropical
jet along and south, and polar jet along and north). While CAMs
have struggled with the rapid evolution of convection in this
highly dynamic environment, observational trends (and most
helpfully the rapidly updating experimental WoFS system) suggest
that additional localized 3-5" totals are likely over the next few
hours. Scattered to numerous instances of flash flooding are
likely, and may be locally significant and life threatening (given
3-hr Flash Flood Guidance as low as 1.5-2.0" and prior high totals
partially overlapping the MPD).

Churchill

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_obl-6YcNFk9HM5yYk1s_xg7h9gDxuAyBo6BNj7PIMO5wp3UJFGie6VqtxAlcSzFJk0f= t7fCfZeVEwD4iLBuNqFUCSw$ for graphic product...

ATTN...WFO...FWD...LZK...OUN...SGF...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 36609217 36389116 35599154 34749251 33969369=20
33519493 33369602 33479696 33579721 33979734=20
34539667 35259583 35769516 36139470 36419423=20
36559356 36589295=20

=3D =3D =3D
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AWUS01 KWNH 200206
FFGMPD
INZ000-ILZ000-MOZ000-200705-

Mesoscale Precipitation Discussion 0293
NWS Weather Prediction Center College Park MD
1005 PM EDT Mon May 19 2025

Areas affected...Central and Southern MO...Central and Southern IL

Concerning...Heavy rainfall...Flash flooding likely

Valid 200205Z - 200705Z

SUMMARY...Increasing coverage of showers and thunderstorms with
high rainfall rates along with areas of cell-training will likely
result in scattered to numerous areas of flash flooding overnight.
Locally significant and life-threatening urban flash flooding
impacts will be possible.

DISCUSSION...A well-organized band of heavy showers and
thunderstorms with very cold convective tops continues to
generally expand in coverage across central and southern MO with
additional cells seen in radar imagery beginning to develop also
farther east across eastern MO and small portions of western IL.

All of this continues to evolve as a very strong warm-air
advection pattern advances across the middle MS Valley and into
the lower OH Valley with enhanced moisture and instability
transport seen focusing up along and over a warm front. MLCAPE
values are as high as 2000 to 3000 J/kg from central and southern
MO through southern IL involving the warm sector, and the
environment is very moist and strongly sheared with PWs of 1.6 to
1.8+ inches and effective bulk shear values of 50+ kts. As a
result, the convective mode is inclusive of supercell
thunderstorms, and the latest radar shows a number of embedded
supercells within the broader axis of convection.

Over the next several hours, areas of significant cell-training
will be a concern across areas of southern and eastern MO and into
southern IL where radar trends along with recent hires model
guidance supports the convection becoming increasingly aligned
with the deeper layer southwesterly flow across the region.

The latest HRRR, RRFS and experimental WoFS guidance all support
high rainfall rate potential with the evolution of the supercell
thunderstorm activity over the next few hours with rainfall rates
reaching as high as 2.5 inches/hour, and this is certainly
supported by the highly favorable thermodynamic and kinematic
environment that is in place.

Cell-training will likely favor some storm totals of 3 to 5 inches
with isolated heavier totals to 6+ inches possible. This will
likely result in scattered to numerous areas of flash flooding
which will include the potential for significant and
life-threatening urban flash flooding impacts.

Orrison

...Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!66kuZVZ6W0BjlOXg3oPFMYzM38EtDM2KnSaaV6CzYZ3fWpFETgG2mSJduUdnVmA4_ezm= 7hcNUjDEnTNXU3BgWBAF1DU$ for graphic product...

ATTN...WFO...ILX...LSX...PAH...SGF...

ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC...

LAT...LON 40338905 39488773 37988803 36669033 36519312=20
37399357 39109227 40159086=20

=3D =3D =3D
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