Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Aug 25 2023 00:09:50

AWUS01 KWNH 250009
FFGMPD
OHZ000-MIZ000-INZ000-250606-

Mesoscale Precipitation Discussion 0972
NWS Weather Prediction Center College Park MD
809 PM EDT Thu Aug 24 2023

Areas affected...Lower Michigan into northern Ohio

Concerning...Heavy rainfall...Flash flooding likely

Valid 250006Z - 250606Z

Summary...Storms are forming along a surface boundary in the
central part of Lower Michigan currently.  These storms will
continue to grow in coverage an intensity while migrating toward
areas that experienced extensive flash flood impacts early this
morning.  Flash flooding is likely in this scenario.

Discussion...Robust convection continues to deepen along a surface
front located roughly from near Milwaukee to near Saginaw.  Along
and south of that boundary, near 80F dewpoints beneath 7.5+ C/km
lapse rates were contributing to extreme instability (4000+ J/kg
MLCAPE) and areas of 2+ inch PW values were contributing to
efficient rainfall processes beneath the storms.  One drawback for
heavier rainfall so far appears to be appreciable mid/upper flow
(30-45 knots) that was contributing to near 30 knot storm motions
along portions of the front.  Even with these motions, localized
backbuilding has contributed to spots of 1+ inch/hr rain rates
(especially northwest of Saginaw), and continued backbuilding/cell
mergers should continue to foster 1+ inch/hr rain rates from time
to time as storms migrate southeastward.

Of particular concern is the ground conditions across portions of
southeastern Michigan and Ohio.  Areas of 4-6 inch rainfall totals
last night through early this morning resulted in widespread flash
flood impacts, and ground conditions are still wet and conducive
to excessive runoff.  Areas of 1+ inch/hr rates will overspread
these areas and overcome low FFG thresholds (around 0.5-1
inch/hr), likely resulting in flash flooding.  Based on latest
trends, an uptick in flash flood potential will materialize across
southeastern Michigan (including Detroit Metro) as early as 02Z
before spreading into northern Ohio from around 03-04Z onward.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!4rdqYP7tNvM8FxvgmXlNEIvRVYC1gQEnHeEjaInsPKo3G14ip-TCJZ8c0_6a5BVNZ4yu=
S09UrC5vs9_bc5IsLINap3M$  for graphic product...

ATTN...WFO...APX...CLE...DTX...GRR...IWX...PBZ...

ATTN...RFC...NCRFC...OHRFC...NWC...

LAT...LON   43978477 43858296 42848199 42388134 41648055=20
            40898069 40838232 41058445 41858631 43408615=20
=20=20=20=20=20=20=20=20=20=20=20=20

=3D =3D =3D
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