Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Aug 01 2025 18:06:50

AWUS01 KWNH 011806
FFGMPD
SDZ000-NDZ000-MTZ000-020005-

Mesoscale Precipitation Discussion 0841
NWS Weather Prediction Center College Park MD
205 PM EDT Fri Aug 01 2025

Areas affected...portions of South Dakota

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

Valid 011805Z - 020005Z

Summary...An incoming mesoscale convective vortex (MCV) is
expected to lead to a convective uptick shortly as remaining CIN
erodes.  Hourly rain amounts to 2.5" with local totals to 4" are
expected later this afternoon, which could lead to isolated to
widely scattered instances of flash flooding.

Discussion...Cumuli are becoming agitated along an axis of
cyclonic wind turning ahead of an incoming (eastward-moving) MCV
across northwest SD.  SPC mesoanalyses show CIN eroding.=20
Precipitable water values are approaching 1.5".  MLCAPE is
500-1000 J/kg, and increasing around 200 J/kg per hour due to
solar insolation.  Effective bulk shear is 25-35 kts.

The 12z HREF and 06z REFS show disagreement as to when and where
convection should break out in the vicinity of the MCV or along
the nearby surface trough, with the HREF showing sooner initiation
than the REFS.  Based on SPC mesoanalyses and recent veggie band
imagery, believe it would be sooner rather than later.  Given the
parameters available, organized convection with hourly rain
amounts to 2.5" and local totals to 4" are supported, which fits
in well with 12z ARW, 00z NSSL WRF, 12z hi-res NAM, and to a
limited degree 12z Canadian Regional runs.  As the area has been
dry over the past week, the main issues from this rainfall are
expected to be urban.  Isolated to widely scattered instances of
flash flooding appear possible through 00z/7 pm CDT.

Roth

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!7BpQFMtE4CNpXWFNBSxg48b2uYJ_WmcEAp692mFvHiw9-IRS7cAnA33uVqwKQiRc6vqv=
2iypithuscEreudpdFp56ZM$  for graphic product...

ATTN...WFO...ABR...BIS...BYZ...FSD...UNR...

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

LAT...LON   45980371 45830072 44589880 43069805 43439929=20
            44130099 44870328 45310406=20

=3D =3D =3D
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