Saturday, July 20, 2019

Mesoscale Discussion for McHenry Co., IL

<pre>ACUS11 KWNS 201900
SWOMCD

Mesoscale Discussion 1546
NWS Storm Prediction Center Norman OK
0159 PM CDT Sat Jul 20 2019

Areas affected...Portions of northern Illinois and Chicagoland Area

Concerning...Severe potential...Watch possible

Valid 201859Z - 202100Z

Probability of Watch Issuance...40 percent

SUMMARY...As thunderstorms/outflow near northern Illinois, intense
convection is possible given the extreme buoyancy in the area.
Uncertainty remains as to how far south ongoing/newly developing
convection will push into northern Illinois. A WW is possible should
convective trends become more clear.

DISCUSSION...A relatively narrow corridor of undisturbed airmass
remains in far southern Wisconsin and northern Illinois.
Temperatures have risen into the upper 80s F to low 90s F with
dewpoints holding in the upper 70s F. Two ongoing linear segments in
southwestern and southeastern Wisconsin will likely continue to sag
slowly southward with time. Given the extreme buoyancy -- MLCAPE of
4000+ J/kg -- intense convection is possible with damaging winds
being the primary threat. With the low-level shear vector oriented
nearly parallel to the outflow, it is uncertain how much development
will occur southward into Illinois. However, HCRs are currently
visible on visible satellite imagery in northeastern Illinois. Even
subtle lift from the outflow boundary may allow parcels to reach
their LFC. A WW is possible should trends reveal convection is more
likely.

..Wendt/Guyer.. 07/20/2019

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

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

LAT...LON 42759010 42888985 42888822 42588786 42248785 42028799
41738852 41748940 41928995 42139022 42269032 42429028
42759010 </pre>


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