Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Apr 20 2023 19:45:11

AWUS01 KWNH 201945
FFGMPD
LAZ000-MOZ000-ARZ000-TXZ000-OKZ000-210143-

Mesoscale Precipitation Discussion 0200
NWS Weather Prediction Center College Park MD
343 PM EDT Thu Apr 20 2023

Areas affected...Much of AR...South-Central MO...Far Southeastern
OK...Far Northwestern LA...Portions of Northeast TX

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

Valid 201943Z - 210143Z

Summary...Hourly rates as high as 1-2"/hr may result in localized
near-term totals of 2-3"+. Isolated instances of flash flooding
are possible.

Discussion...A cold front is slowly moving east from the Southern
Plains into the Lower MS Valley this afternoon and evening, with
deeper convective activity beginning to along and ahead of the
front (with convection ahead of the front associated with a
pre-frontal trough). Deep layer moisture flux convergence has
increased significantly over the past 2-4 hours (per SPC RAP
mesoscale analysis), with the mesoscale environment currently
characterized by precipitable water values of 1.0-1.5 inches (near
the 90th percentile, per SPC sounding climatology), SB CAPE of
1000-2500 J/kg, and effective bulk shear of 30-40 kts. In
addition, the right-entrance region of a 120 kt jet streak is
moving into the area, providing additional large-scale lift via
divergence aloft. So far convective storm modes have been rather
discrete with supercell and multicell clusters, but the forcing of
the front should allow storms to orient linearly with deep layer
unidirectional flow favoring a northeasterly motions (generally
averaging 20-30 kts, via both the 0-3 km mean wind and Bunkers
right motions). This may result in some localized training given
the slow progression of the front, and additional convection
forming along the pre-frontal trough may also help to prime soils
for isolated instances of flash flooding.

Ongoing storms across the region are already capable of localized
rates as high as 1.0-1.5"/hr, and these rates may increase to as
high as 1.5-2.0"/hr locally (particularly farther south into the
ArkLaTex, where instability is maximized). This could result in
near-term, 2-3 hourly totals as high as 2-3"+ locally.. which is
approaching corresponding flash flood guidance (FFGs) for much of
Arkansas. Farther south into the ArkLaTex, FFGs are closer to 3-4"
and will be harder to realize (though the 12z HREF neighborhood
exceedance probabilities for 3"/3-hr are as high as 20-30% in this
region).

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!8WgijGLOZfsJcddt_-xOgpAsvRkxeokMQfPCIKifCNDUa-lhXEIacUg1ND_Vgr0csO40=
bkqc5mWSC88O781hBYqSsH0$  for graphic product...

ATTN...WFO...FWD...LSX...LZK...MEG...OUN...PAH...SGF...SHV...
TSA...

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

LAT...LON   37679158 36839045 35729098 35209139 34799177=20
            34149237 33749270 32789376 32219481 32179567=20
            32259632 32909685 33559636 34589539 35389468=20
            36469395 36979352 37669275=20

=3D =3D =3D
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