Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu May 11 2023 20:58:13

AWUS01 KWNH 112058
FFGMPD
NEZ000-SDZ000-WYZ000-120256-

Mesoscale Precipitation Discussion 0265
NWS Weather Prediction Center College Park MD
457 PM EDT Thu May 11 2023

Areas affected...far western Nebraska, eastern Wyoming,
southwestern South Dakota

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

Valid 112056Z - 120256Z

Summary...Increasing convection along and just east of a surface
trough could pose a flash flood risk over the next several hours.

Discussion...Recent radar/satellite indicates an uptick in
convective coverage an intensity over the last 1-2 hours.  The
cells are in an environment characterized by weak to moderate
instability (500-1500 J/kg SBCAPE), with moisture/instability
being bolstered by warm/moist low-level advection and insolation
upstream over Nebraska.  Low-level flow veers to southerly aloft,
allowing for northward/north-northwestward storm motions and a
favorable scenario for axes of training.  The training/prolonging
of heavier downpours should bolster rain rates into the 1-1.5
inch/hr range especially in the 22Z-03Z timeframe.

The downpours should fall over areas that appear to be sensitive
to heavy rainfall.  FFG thresholds across the region are currently
in the 1-2 inch/hr range (lowest in southwestern South Dakota, and
these thresholds should be eclipsed on occasion through the early
evening.

Models/CAMs suggest that the peak of the convective threat across
the region could exist between 00Z-03Z, with several areas of
two-inch rain amounts expected.  Although most of the convection
should be aided by diurnal forcing, lingering heavy rainfall
should occur after sunset - and potentially beyond the 03Z
timeframe.  Eventually, however, instability should wane as
convective overturning and nocturnal boundary layer stabilization
occurs especially after 02Z.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!69Y-63aL7VBJiBC-ePqfVB28Sc89Z39E81KXDtsfMiLdKwp32NEfChFwgB3lRKuID7T_=
bC5PDzaHrhz_XZ0KXfqR6zU$  for graphic product...

ATTN...WFO...CYS...LBF...UNR...

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

LAT...LON   44580279 44250236 43820234 42980264 42410257=20
            41680266 41290312 41520412 42450416 43640408=20
            44500387=20

=3D =3D =3D
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