Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Sep 18 2025 00:26:15

AWUS01 KWNH 180026
FFGMPD
MNZ000-SDZ000-180524-

Mesoscale Precipitation Discussion 1099
NWS Weather Prediction Center College Park MD
825 PM EDT Wed Sep 17 2025

Areas affected...eastern South Dakota, far western Minnesota

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

Valid 180024Z - 180524Z

Summary...A fairly focused band of slow-moving convection is
producing rain rates exceeding 1.5 inches/hr.  Areas of excessive
runoff and flash flooding are expected.  This risk should persist
through around 05Z/midnight CDT.

Discussion...A fairly focused band of convection was pivoting
slowly westward on the eastern periphery of a surface low center
south of Pierre, SD.  This band extended from just north of Huron,
SD eastward to just west of Marshall, MN.  This band was also
collocated with focused low-level convergence and a stationary
front in the area.  South of the front, areas of 500-1000 J/kg
SBCAPE and 1.5 inch PW values were promoting updrafts with
efficient rainfall processes.  With convection slowly moving and
focused along the nearly stationary front, spots of 2 inch/hr rain
rates were being estimated per MRMS.  These rain rates were
persisting in local areas for some time, likely causing at least
isolated runoff concerns.

Models generally depict that this scenario will not change much
over the next 3-5 hours.  Instability south of the boundary will
only be slowly exhausted with boundary layer cooling.  Spots of
1-2 inch/hr rain rates are likely to continue, and isolated areas
could experience total amounts of 3-5 inches over the next few
hours.  Convection should only gradually weaken after 05Z or so.=20
Flash flooding is possible in a localized basis in this scenario.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_AlqbLxOJ3EYu3kmeAcfrfTm2Nb6SDNqDlb-bOUepbeMHIzPk6C-Xu_djkN0NFkB5aBL=
PYfckMWEw00GGln7F4EhZUo$  for graphic product...

ATTN...WFO...ABR...FSD...MPX...

ATTN...RFC...KRF...MSR...NWC...

LAT...LON   45229781 45229552 44589504 44109618 43799983=20
            44939977=20

=3D =3D =3D
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