Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Oct 13 2023 05:58:31

AWUS01 KWNH 130558
FFGMPD
NEZ000-SDZ000-131000-

Mesoscale Precipitation Discussion 1147
NWS Weather Prediction Center College Park MD
157 AM EDT Fri Oct 13 2023

Areas affected...northeastern NE...southeastern SD

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

Valid 130600Z - 131000Z

Summary...Localized rainfall rates of 1-2"/hr may result in
isolated instances of flash flooding overnight.

Discussion...A narrow deformation zone on the northeastern
quadrant of a maturing low pressure system has resulted in
localized heavy rainfall late tonight, situated across
northeastern NE and far southeastern SD. Rainfall rates are
estimated to have increased to as high as 2"/hr locally (per
MRMS), and this activity may continue with very little movement
for the next several hours (as elevated deep layer moisture flux
convergence remains anchored to the northeast of the nearly
stationary surface low pressure). The mesoscale environment is
characterized by MU CAPE of 500-1000 J/kg, PWATs of 0.8-1.0 inches
(near the 75th percentile, per OAX sounding climatology), as well
as strong 850 mb warm air advection and 925 mb frontogenesis.

While the HRRR has been rather inconsistent with hourly runs since
23z, the 00z run itself had a fairly strong depiction of localized
1-3" accumulations in association with this localized deformation
zone. Of the 00z HREF suite, the ARW member also had a similar
depiction in the area where localized heavy rainfall has already
manifested. Both of these pieces of guidance depict the rainfall
peaking over the next 1-3 hours, and associated HREF 40-km
neighborhood derived products show relatively high probabilities
(15-30%) for 3" exceedance (corresponding with both 6-hr FFG and
10-yr ARI exceedance thresholds as well). With FFGs as low as 2-3"
in this localized region of northeast NE and far southwest SD,
isolated instances of flash flooding are possible.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7ml-WS0KCUAaz5Jrv4UkU14zj5uXCiPZA5uGmbz5nIEceuOaHv2ioTVYwn3V3NH5_mQH=
x-mTWS-4iG8_PpqS-v0deqA$  for graphic product...

ATTN...WFO...FSD...LBF...OAX...

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

LAT...LON   43169806 42739743 42289736 42019793 42289855=20
            42449905 43089896=20

=3D =3D =3D
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