Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Aug 20 2024 04:03:13

AWUS01 KWNH 200403
FFGMPD
SDZ000-NDZ000-MTZ000-WYZ000-201000-

Mesoscale Precipitation Discussion 0909
NWS Weather Prediction Center College Park MD
1202 AM EDT Tue Aug 20 2024

Areas affected...portions of South Dakota

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

Valid 200400Z - 201000Z

Summary...Scattered thunderstorm activity will continue to
increase in coverage over the next 3-6 hours.  A few instances of
convective training are expected, which could result in areas of
1-2 inch/hr rain rates.  Flash flood potential exists through at
least 10Z.

Discussion...Latest radar mosaic imagery indicates a series of
training supercells just north of Rapid City.  These storms were
on the eastern edge of very steep mid-level lapse rates (promoting
intense updrafts) and were also beginning to interact favorably
with a strong (30-35 kt) low-level jet across western SD.=20
Additional cells were beginning to deepen across north-central
South Dakota under the influence of weak mid-level shortwave
troughing across the region.  Models depict that a gradual, yet
continued expansion in convective coverage should occur across the
region through the next 3-5 hours or so.

As this occurs, weak westerly flow aloft will allow for modest
storm motions (around 10-20 knots).  Furthermore, the orientation
of any thunderstorm development could favor additional convective
training and at least a few areas of 1.5-2 inch/hr rain rates at
times.  These rain rates will exceed local FFG thresholds
(currently in the 1.5 inch/hr range), resulting in potential for
excessive runoff and flash flooding.  There is some potential for
cells to congeal and grow upscale later tonight, although an
isolated flash flood risk should continue in that regime
especially where mergers/training can materialize.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4cs-IlS3TfxAHcVoe_9Cs2YTGgJZjTvO7QDCOJm2REV_Ql7fR-mcj7tM23dy1qXdUv-Y=
jjRoOuBb28R7cweqOmuO7rs$  for graphic product...

ATTN...WFO...ABR...BIS...BYZ...FSD...UNR...

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

LAT...LON   46030236 45919945 44239859 43769895 43230027=20
            43030292 43380377 44510424 45640379=20

=3D =3D =3D
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