948
AWUS01 KWNH 250346
FFGMPD
TNZ000-KYZ000-MSZ000-MOZ000-ARZ000-TXZ000-OKZ000-250945-

Mesoscale Precipitation Discussion 0320
NWS Weather Prediction Center College Park MD
1145 PM EDT Fri May 24 2024

Areas affected...much of AR and surroundings into the Mid-South

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

Valid 250345Z - 250945Z

Summary...Mesoscale convective system (MCS) will continue to
produce hourly accumulations of 1-2" overnight likely resulting in
localized totals of 2-5", scattered instances of flash flooding.

Discussion...An MCS has taken shape over central and southern AR
late this evening, consisting of a complex mix of storm modes with
embedded supercells, surging bow echos, and backbuilding multicell
clusters. The most intense component as of late is a northeastward
rapidly propagating bow echo, possibly the result of an earlier
storm split (favoring the left-mover vector, as upwind and
downwind propagation vectors favor a southwesterly propagation).
Out ahead of this newly propagating bow echo, earlier storms that
formed and followed a southeasterly motion have produced localized
totals of 2-4" over portions of the MS Delta/Alluvial Plain. FFGs
have been diminished as a result of this earlier precipitation,
generally ranging from 1.5-2.5"(for 3-hr period) over more
sensitive soils (and a bit higher at 2.0-3.0" over the less
saturated soils of northeast AR and southwest TN). With expected
peak hourly accumulations of 1-2", new (or renewed) instances of
flash flooding should be easily achieved. The mesoscale
environment clearly will continue to support storms through a good
portion of the overnight period with instability little diminished
(ML CAPE ranging from 2000-3000 J/kg), PWATs at near record levels
for late May (per SPC sounding climatology with a range of
1.5-1.9"), effective bulk shear of 35-45 kts, and moderate
moisture transport via a locally strong (25-30 kt) LLJ.

Fresh 00z HREF guidance is handling the convective activity
reasonably well, though the HRRR in particular is struggling to
properly initialize the core of the strongest convection. That
said, the 40-km neighborhood probability fields for 2" and 3"
thresholds is rather impressive (through 09z), indicating 20-60%
and 15-35% maximized probabilities over much of the Mid-South.
Given the observational trends, highly favorable parameter space,
and relatively sensitive soils, scattered instances of flash
flooding are considered likely (with localized totals of 3-5"
expected over the Mid-South, i.e. the red hatched area, and 1-3"
localized totals generally expected elsewhere within the MPD).
Convection is expected to be fading across the area by 10z as
instability is gradually exhausted.

Churchill

...Please see www.wpc.ncep.noaa.gov for graphic product...

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

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

LAT...LON   37099085 36228874 34288902 33359078 33139161
            33069259 33139380 33369431 34079476 35689450
            36479316