ZCZC SPCSWOMCD ALL
ACUS11 KWNS 290634 
SPC MCD 290634 
INZ000-ILZ000-WIZ000-290800-

Mesoscale Discussion 1384
NWS Storm Prediction Center Norman OK
0134 AM CDT Thu Jul 29 2021

Areas affected...Portions of southeastern WI and northeastern
IL...including Chicago

Concerning...Severe Thunderstorm Watch 399...400...

Valid 290634Z - 290800Z

The severe weather threat for Severe Thunderstorm Watch 399, 400
continues.

SUMMARY...The greatest threat for 60-75 mph wind gusts and perhaps a
tornado will likely focus across portions of southeastern Wisconsin
and northeastern Illinois in the short term.

DISCUSSION...Radar imagery from KMKX has recently shown a bookend
vortex with at least one prior CC minimum moving from Jefferson into
Waukesha counties in southeastern WI around 0615-0630Z. With ample
low-level shear still present ahead of the ongoing MCS across
southern WI and to the south of a warm front located over Lake
Michigan and Lower MI, a threat for a tornado or two embedded within
the MCS will likely persist in the short term. Otherwise, scattered
severe/damaging winds of 60-75 mph will impact a greater portion of
southeastern WI into northeastern IL, as 1500-2500 J/kg of MLCAPE
and a rich low-level airmass are present across this area. The apex
of the bow appears to be moving southward around 35-45 kt, and the
overall severe threat is expected to increase across northeastern
IL, including the Chicago metro, over the next couple of hours (by 3
AM CDT).

..Gleason.. 07/29/2021

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

ATTN...WFO...LOT...MKX...

LAT...LON   42808935 41968929 41568849 41568753 41848747 42308771
            42728768 42958767 43178824 42948870 42808935 

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