AWUS01 KWNH 252247
FFGMPD
FLZ000-GAZ000-ALZ000-260445-

Mesoscale Precipitation Discussion 1058
NWS Weather Prediction Center College Park MD
646 PM EDT Wed Sep 25 2024

Areas affected...Florida Panhandle into Central Georgia

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

Valid 252245Z - 260445Z

SUMMARY...Particularly heavy rain is expected in southwest Georgia
into the Florida Panhandle this evening due to convergence of
pre-frontal activity from the west and the outermost banding of
Helene from the south. Flash flooding is likely despite dry
preconditions due to extreme rainfall rates of 3" per hour.

DISCUSSION...Heavy and locally excessive pre-frontal activity over
southeast AL and west-central GA is shifting east on outflow while
the outermost bands of Helene have been tracking north over the FL
Peninsula. Convergence of these two areas is progged this evening
over southwest Georgia into the FL Big Bend/eastern Panhandle.
This outer band is on the leading edge of particularly high
moisture, lining up with the 2.2" PW contour from recent RAP
analysis with PW climbing to 2.4" farther down the Peninsula which
is 2.5 sigma over normal. Sufficient instability is present with
MLCAPE of 1000 to 1500 J/kg.

Recent HRRR runs have been under realizing rainfall rates which
are estimated from KTLH and KVAX over Thomas County, GA. However,
the timing in recent HRRRs has been decent with the main
convergence over southwest GA occurring between 00Z and 02Z. There
is a risk for 2 to 5" rainfall through the rest of the evening
which is only a little above the high 3hr FFG of 4 to 5" due to a
lack of rain in this part of GA yet. However, these extreme rates
from slow moving and merging cells warrants likely wording for
this discussion.

A trough extending southwest from western GA extends over the FL
Panhandle and should provide a focus for some additional heavy
rain, so the discussion area is extended west about halfway
through the Panhandle. As of now the area west of Apalachee Bay
which received heavy rain earlier today appears to be south of the
main heavy rain risk area, but given this coast is in the main
Helene moisture plume there is at least a localized excessive
rainfall risk there.

Further banding from Helene approaches this area overnight, so
expect further MPDs tonight and through the passage of Helene
Thursday night.

Jackson

ATTN...WFO...BMX...FFC...JAX...MOB...TAE...

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

LAT...LON 33338324 32558294 30998309 30018392 29348506
30198636 30938639 31758554 32598502 33278448

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