Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jul 28 2023 20:34:47

AWUS01 KWNH 282034
FFGMPD
MIZ000-INZ000-WIZ000-ILZ000-IAZ000-290245-

Mesoscale Precipitation Discussion 0802
NWS Weather Prediction Center College Park MD
433 PM EDT Fri Jul 28 2023

Areas affected...near the IL/WI border into northern IN

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

Valid 282045Z - 290245Z

Summary...Shower and thunderstorm development will develop soon
near a front and returning outflow boundary.  Hourly rain totals
to 2.5" with local amounts to 5" could lead to flash flooding.

Discussion...SPC mesoanalyses over the past several hours reveal
that CIN across the region is eroding in the wake of the
convective system heading across WV.  An upper level shortwave
extending from WI and central IA is moving eastward, aiding upper
level divergence across the discussion area.  Veggie band
satellite imagery reveals a cumulus field forming near the MN/IA
border east-southeast to the WI/IL border, supporting the SPC
mesoanalysis.  This is near and to the northeast of a low pressure
area and a mesoscale warm front/returning outflow boundary.  ML
CAPE is rising ~500 J/kg per hour, now over 4500 J/kg over
northern IL.  Effective bulk shear of 25-45 kts lies across the
region.  Precipitable water values per GPS data are 1.6-1.8".=20
Diffluence in the 1000-500 hPa thickness pattern is fairly
pronounced in this region.  All of the above support the formation
or expectation of an organized convective complex in the near
future.

The expectation in the short term is for showers and thunderstorms
to develop from near the IA/WI/IL border east and east-southeast
into northern IN with time and eventually develop into an
organized convective complex.  The mesoscale guidance has a varied
signal in this region which lowers confidence in details, hence
the Possible category.  The GFS-based Galvez-Davison instability
Index implies an increase in thunderstorm development to at least
a scattered coverage between now and 03z.  The ingredients
available support hourly rain totals to 2.5" with local amounts to
5".  This would occur where cells train, merge, or mesocyclones
manage to form.  This rainfall would be especially problematic in
urban areas and near the WI/IL border, which is a region that has
received 300% of their normal rainfall over the past week.=20
Isolated to widely scattered instances of flash flooding are
anticipated.

Roth

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!5ZF6-sOl3Mh97ERSO5yqhyrTT3oFzQvvJDiQnwqs6ilTTg3L9zl0npy7ArX_uPIWYOn3=
o9GpTSu9vvf8dI-eZq7g5io$  for graphic product...

ATTN...WFO...ARX...DVN...GRR...IWX...LOT...MKX...

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

LAT...LON   43348945 42718718 41358500 40728534 40968732=20
            41708941 42579099 43269104=20

=3D =3D =3D
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