Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Aug 22 2025 06:03:35

AWUS01 KWNH 220603
FFGMPD
MNZ000-SDZ000-221200-

Mesoscale Precipitation Discussion 0972
NWS Weather Prediction Center College Park MD
202 AM EDT Fri Aug 22 2025

Areas affected...central and eastern SD into some adjacent
portions of MN

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

Valid 220600Z - 221200Z

Summary...Training and repeating of very heavy rainfall (up to
2-4"/hr rates) may lead to isolated to scattered instances of
flash flooding overnight.

Discussion...Discrete convection is beginning to backbuild and
proliferate this evening, in the vicinity of a sharp baroclinic
zone with strong low-level frontogenesis. The mesoscale
environment is otherwise characterized by MLCAPE of 1000-2500
J/kg, PWs of 1.2-1.5" (near the 90th percentile, per ABR sounding
climatology), and effective bulk shear of 35-45 kts. While
steering flow is relatively strong at 20-30 kts towards the ESE
with Corfidi vectors favoring southward propagation, current
storms are anchored in the boundary layer near where low-level
convergence is maximized with backbuilding towards the west
favoring training/repeating of very heavy rainfall (with MRMS
estimates indicating rates as high as 2-4"/hr).

Latest hi-res guidance (00z HREF suite) is in remarkably good
agreement with regard to the spatial axis of heavy rainfall,
located in excellent proximity to where convection has
proliferated. While the guidance is not in as good agreement with
regard to the intensity of convection, the HREF does still
indicate the extreme potential well with probabilities for 3" and
5" exceedance of 40-50% and 5-10%, respectively (with the 00z ARW2
and NAM-nest being the most aggressive in depicting 3-5" totals,
along with some recent hourly runs of the experimental RRFS).
Isolated to scattered instances of flash flooding are possible
(with 3-hr FFGs generally ranging from 1.5-2.5" and associated
HREF FFG exceedance probs of 30-40%), though impacts to life and
property will likely be rather limited given how rural/sparsely
populated the region is.

Churchill

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!62MjQZu1P30gFyRVFCIkljS7l3mHwOxLYzCOgJ7Dhz2d6bPgwec8ea20I81V77QKnax1=
MBzyilZJvirpO1vs87e3uGc$  for graphic product...

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

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

LAT...LON   45309819 44869613 43889656 43699801 44049944=20
            44800116 45270021=20

=3D =3D =3D
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