AWUS01 KWNH 041056
FFGMPD
ILZ000-MOZ000-ARZ000-041545-

Mesoscale Precipitation Discussion 1121
NWS Weather Prediction Center College Park MD
555 AM EST Mon Nov 04 2024

Areas affected...northern AR into south-central/southeastern MO,
southwestern IL

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

Valid 041052Z - 041545Z

Summary...Areas of training heavy rain will continue to pose a
possible threat for flash flooding across parts of northern AR
into south-central/southeastern MO through 15Z. Portions of
southwestern IL may also see impacts. Rainfall rates of 1-2 in/hr
(locally higher) should be expected.

Discussion...10Z surface observations showed an elongated outflow
boundary extended southwestward from the southern IL/MO border
into northwestern AR and southeastern OK. Training and repeating
rounds of thunderstorms were occurring along and just north of the
outflow boundary from northwestern AR into southern MO, with
MRMS-derived peak rainfall rates of 1.0-1.5 in/hr. Area VAD wind
plots of 850 mb winds showed 40-50 kt in place from Fort Smith to
Memphis, overrunning the boundary and allowing training of heavy
rainfall echoes given similarly oriented steering flow from the
SSW. There was a gradient in MLCAPE across AR, with 10Z SPC
mesoanalysis data showing 1500 j/kg along the OK/AR border,
weakening to the east with less than 500 J/kg along the AR/TN
border, with elevated instability only marginally greater to the
north.

There is little change expected to the regional pattern in place
over the next 3-6 hours, with 850 mb winds of 40-50 kt forecast by
the RAP to continue through 15Z, along with similar instability
and broad/weak diffluent flow aloft. While convective overturning
may moderate current instability values a bit with time,
orographic ascent will enhance low level lift across the southern
Ozark Plateau. Expectations are for occasional areas of training
to setup from northern AR into south-central and southeastern MO,
producing 1-2 in/hr rainfall rates as these relatively strong low
level winds overrun the well-defined outflow boundary in place.
Flash flooding will remain possible for at least another few hours.

Otto

ATTN...WFO...LSX...LZK...MEG...PAH...SGF...TSA...

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

LAT...LON 38518998 38458936 38288912 37378937 36069137
35239281 34989325 34979377 35129412 35189422
35629435 36219404 36999323 38339078

$$
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