Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Jul 29 2023 06:35:54

AWUS01 KWNH 290635
FFGMPD
MIZ000-291000-

Mesoscale Precipitation Discussion 0807
NWS Weather Prediction Center College Park MD
235 AM EDT Sat Jul 29 2023

Areas affected...central Lower Michigan

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

Valid 290633Z - 291000Z

Summary...Bands of deep convection will move slowly across central
Michigan this morning.  Areas of 1-2 inch/hr rain rates could
cause a few spots of excessive runoff through 10Z.

Discussion...A mature MCS has crossed Lake Michigan and is
producing heavy rainfall across west-central Lower Michigan from
just north of Grand Rapids to just west of Saginaw currently.  The
MCS is interacting with a moist, marginally unstable downstream
airmass (1.7 inch PW values and 500 J/kg MLCAPE, respectively) to
support deep updrafts in east-to-west orientation.  With its
orientation parallel to flow aloft and slow movement, areas of 1-2
inch/hr rain rates have materialized, and these rates are
approaching local FFG thresholds (1.5-2 inches/hr) and could cause
potentially excessive runoff.  Flash flood potential will exist
with this activity in the short term.

While the longevity of this flash flood threat is unclear, the
well-organized nature of the MCS, it's proximity to a stationary
surface boundary, and instability downstream suggests that storms
could persist for at least another 3-4 hours while migrating
slowly eastward across the state.  This should result in a few
areas of 3 inch rainfall totals (including 1-2 inch/hr rain rates)
persisting through 10Z.  Given the aforementioned scenario, flash
flooding is possible especially where heavier rainfall can
materialize across urbanized and/or locally sensitive areas.

Cook

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9IYHE0-VbLIFB2B6eznEIGQSn1_AbkD6FiAsxut3Kok8md3EOL-PRKZiNLyjncxx9qbI=
tM4Cy2eN6viQJBfmR02jits$  for graphic product...

ATTN...WFO...APX...DTX...GRR...

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

LAT...LON   44298437 43928268 43088226 42538267 42358362=20
            42438445 43118569 44008536=20

=3D =3D =3D
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