Saturday, July 20, 2019

Mesoscale Discussion for McHenry Co., IL

<pre>ACUS11 KWNS 202158
SWOMCD

Mesoscale Discussion 1550
NWS Storm Prediction Center Norman OK
0458 PM CDT Sat Jul 20 2019

Areas affected...Northern Illinois

Concerning...Severe Thunderstorm Watch 532...

Valid 202158Z - 202300Z

The severe weather threat for Severe Thunderstorm Watch 532
continues.

SUMMARY...The greatest severe weather threat remains along the
Illinois lake shore in WW 532.

DISCUSSION...The severe threat has likely waned in the near term in
western portions of severe thunderstorm watch 532. The primary
severe threat is now along the Lake Michigan shoreline in Illinois
where there are ongoing storms and additional development is
expected. Storms continue to develop over the convectively enhanced
cold pool in the southern Great Lakes. Given the extreme instability
(4000+ MUCAPE and steep lapse rate environment (7.5 to 8 C/km),
these storms will continue to pose a threat for both large hail and
damaging winds despite only marginal shear (~25 kts). Expect new
development to continue on the southern and western flank as the
outflow boundaries continue to sag south. This will lead to storms
likely impacting downtown Chicago within the hour. Eventually, the
outflow boundary will likely move far enough south into a more
capped environment which should limit additional development south
of Cook county.

..Bentley.. 07/20/2019

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

ATTN...WFO...LOT...DVN...

LAT...LON 42468919 42488805 42328734 41978693 41688694 41578732
41608791 41658845 41768892 42168942 42468919 </pre>


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