ZCZC SPCSWOMCD ALL
ACUS11 KWNS 290818 
SPC MCD 290818 
MIZ000-INZ000-ILZ000-290945-

Mesoscale Discussion 1385
NWS Storm Prediction Center Norman OK
0318 AM CDT Thu Jul 29 2021

Areas affected...Portions of northern IL/IN and southwestern Lower
MI

Concerning...Severe Thunderstorm Watch 400...

Valid 290818Z - 290945Z

The severe weather threat for Severe Thunderstorm Watch 400
continues.

SUMMARY...A strong to severe wind threat continues in the short
term. Storms should gradually weaken with southward extent across
northern Illinois/Indiana later this morning.

DISCUSSION...Both IR cloud tops and radar echo tops associated with
the ongoing MCS across northern IL have recently warmed and
weakened, respectively. Still, a swath of strong to severe wind
gusts (generally 50-65 mph) and related damage reports have occurred
across the Chicago metro area over the past hour or so. The airmass
downstream of this ongoing convection across northern IL/IN and
southwestern Lower MI becomes less unstable with southward extent,
as both surface temperatures and dewpoints slowly decrease. While a
threat for scattered damaging wind gusts will continue in the short
term across this region, current expectations are for the MCS to
continue gradually weakening over the next couple of hours as it
encounters increasing convective inhibition and less instability.
This evolution appears well supported by the past couple of runs of
the HRRR.

..Gleason.. 07/29/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...IWX...GRR...LOT...

LAT...LON   42088885 41838832 41928777 42078727 42448678 42698615
            42468515 42118509 41618529 41128590 40748691 40698795
            40908877 41208905 41858910 42088885 

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