Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Aug 17 2025 06:06:12

AWUS01 KWNH 170603
FFGMPD
MNZ000-SDZ000-171200-

Mesoscale Precipitation Discussion 0949
NWS Weather Prediction Center College Park MD
203 AM EDT Sun Aug 17 2025

Areas affected...Southern Minnesota...East-central South Dakota...

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

Valid 170600Z - 171200Z

SUMMARY...Slow moving, potentially repeating cells pose 2-4"
totals and possible localized incidents of flash flooding through
the remainder of the overnight period.

DISCUSSION...GOES-E 10.3um IR loop shows expanding cluster of
thunderstorms across SW MN over the last few hours and starting to
become better organized with broadening up/downdrafts;
concurrently while newer development is developing between it and
the downstream clusters in WI/MN/IA Tri-state area.  Additionally,
combined with 3.9um loop, low stratus north of the frontal
boundary across central MN/N WI shows southward cold advection
that is further steepening the isentropes across the frontal
boundary that generally sits across the northern row of counties
in Iowa.  RAP analysis, confirmed by CIRA LPW shows pool of deep
layer moisture with Total PWat values over 2" extending from
northeast SD through SE MN, generally enhanced further west where
flux has been greatest along the nose of the southerly low-level
jet where winds are up to 20-25kt per KFSD VWP vs 15-20kts further
east.  The strong moisture convergence along the steepening
isentropic surface, MLCAPEs of 3000-3500 J/kg, has resulted in a
slightly southward development versus 00z Hi-Res CAMs and recent
HRRR cycles, as such, proximity to stronger orthogonal moisture
flux should support efficient rainfall production with rates of
2"/hr.

Stronger shortwave to the west and exiting one to the east has
resulted in fairly unidirectional but also weaker steering flow
just a bit south of due east and parallel to the frontal boundary.
Mean winds of 10-15kts are expected and should allow for some
potential training, but more likely slow overall cell motion
allowing for a few hours of intense rainfall and pockets of 2-4"
totals.  Stronger LLJ due to the approaching wave over the western
Dakotas suggest upstream convective development is probable later
into the overnight periods far west as the Coteau des Prairies
Plateau, but also intersect with back-building from upstream
cluster/WAA cells in SE MN.  As such, have included portions of SE
MN that were incorporated in MPD 947 for longer valid time toward
12z.=20

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7STG0ZQBcR9jgl17njBbuRM45-xzCK3rQdwkyNG1TqkTolDpUFzKmxTd_1U_fV3ahuRZ=
TOVzwQGN6EDSj8LTIAH8J7s$  for graphic product...

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

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

LAT...LON   45469700 45419560 45269458 44899338 44499251=20
            44019168 43729146 43539186 43579398 43759520=20
            44159650 44619756 44979777 45339764=20

=3D =3D =3D
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