Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Sep 21 2023 13:16:15

AWUS01 KWNH 211316
FFGMPD
IAZ000-NEZ000-SDZ000-211714-

Mesoscale Precipitation Discussion 1088
NWS Weather Prediction Center College Park MD
915 AM EDT Thu Sep 21 2023

Areas affected...far western Iowa, eastern Nebraska, far
southeastern South Dakota

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

Valid 211314Z - 211714Z

Summary...A slow-moving convective complex was producing spots of
2-3 inch/hr rain rates at times.  These rates should continue as
storms move slowly southward across the discussion area, prompting
flash flood potential through 16Z.

Discussion...A persistent, slow-moving MCS has migrated slowly
southeastward away from the Sand Hills vicinity toward an axis
from Sioux Falls to near Norfolk.  With this movement, the MCS has
now produced areas of 2-3 inch/hr rain rates over a few areas
(especially just south of Sioux Falls) that have locally exceeded
FFG thresholds across the region.  The MCS was being maintained by
strong low-level flow on the eastern extent of a 30-kt low-level
jet over central Nebraska, and although stable low-levels are
present, nearly 2000 J/kg MUCAPE exists due to steep lapse rates,
supporting robust updrafts.

Latest model runs suggest that the ongoing complex should continue
on its slow southeastward trek, with potential backbuilding on
it's western flank (generally from Holt to Greeley counties and
vicinity).  Heavy rainfall (and 2+ inch/hr rain rates) are likely
to continue at least on an isolated basis associated with the
progression of the MCS and could reach the US 30 corridor in
east-central Nebraska over the next 2-4 hours.

After 16Z, some slackening and westward shift of low-level flow
could act to weaken the complex over time, although the specific
timing of lessened rain rates/flash flood potential is a bit
uncertain.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9hF3Wqt1BfqM5MAPZKj2xmeWUYsg8tKPY6zFzahvRnNeGvnDq05OwYQVBIBLcwvAMSn3=
L-9yM6qkDVkRIZh9xNVzzZc$  for graphic product...

ATTN...WFO...DMX...FSD...GID...LBF...OAX...

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

LAT...LON   43299717 43259627 42749539 41719546 41249613=20
            41089742 41309865 42399929 42989900 43169808=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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