ACUS11 KWNS 211923
SWOMCD
SPC MCD 211922
ILZ000-WIZ000-IAZ000-212115-

Mesoscale Discussion 2070
NWS Storm Prediction Center Norman OK
0222 PM CDT Fri Aug 21 2026

Areas affected...southwest Wisconsin...far eastern Iowa...and
northern Illinois

Concerning...Severe potential...Watch likely

Valid 211922Z - 212115Z

Probability of Watch Issuance...80 percent

SUMMARY...The threat for damaging wind gusts, large hail, and
perhaps a brief tornado or two is expected to increase through the
remainder of this afternoon. A severe thunderstorm watch will likely
be required in the next 1-2 hours.

DISCUSSION...Recent trends in visible satellite and radar data
indicate incipient thunderstorm development occurring along a cold
front pushing into southwest WI. Additional deepening cumulus is
also noted within the pre-frontal warm sector from east-central into
southeast IA. Another storm has recently intensified along the
outflow boundary from earlier storms east of Rockford, IL. The 18Z
DVN sounding is likely a good representation of the ambient
environment with a moist profile through the lowest 3km AGL largely contributing to MLCAPE of around 2500 J/kg. Moreover, the sounding
featured veering winds with height with 35-40 kt of deep-layer shear
oriented largely perpendicular to the surface front.

Prevailing west to west-northwest low-level winds ahead of the front
may allow for air mass recovery to occur over portions of
south-central WI into north-central IL later this afternoon,
effectively creating a wider warm sector for the ongoing WI storms
to spread southeast. The environment described above appears
supportive of organized storm modes, including supercells with an
attendant risk for mainly large hail initially. While low-level
shear is not expected to be overly strong, some potential exists for
a brief tornado or two, especially with any supercells that can
favorably interact with the outflow boundary.

Latest CAM guidance suggests that an initially more discrete storm
mode will gradually transition to a broken band by late afternoon or
this evening, at which point the threat for damaging wind gusts
would increase.

..Mead/Smith.. 08/21/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!8ZCNa1sIgn9Lq2pRVEdd23O_z7vJsk-VpAt4EQqU0rNAXEBD9uoB5KpJYp8d1IU41GAbg3v6RGbKR5S-arefzoZXyvQ$ for graphic product...

ATTN...WFO...LOT...ILX...MKX...DVN...ARX...

LAT...LON 41259092 42809081 43479025 43188956 42078849 41318806
40808810 40308864 40178918 40188983 40359032 40729091
41259092

MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN


= = =
To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM.
--- scorpsmtpd
* Origin: capitolcityonline.net * KY, USA (1:2320/107)