ACUS11 KWNS 212314
SWOMCD
SPC MCD 212313
ILZ000-WIZ000-IAZ000-220115-

Mesoscale Discussion 2075
NWS Storm Prediction Center Norman OK
0613 PM CDT Fri Aug 21 2026

Areas affected...Parts of northern IL...far southern WI...and far
east-central IA

Concerning...Severe Thunderstorm Watch 610...

Valid 212313Z - 220115Z

The severe weather threat for Severe Thunderstorm Watch 610
continues.

SUMMARY...An increase in thunderstorm intensity is possible during
the next few hours. Damaging winds and large hail are still the main
concerns, though a tornado or two cannot be ruled out.

DISCUSSION...Over the last 30 minutes or so, a couple thunderstorms
have increased in intensity across northern IL and far east-central
IA, as a subtle frontal wave low approaches the area from the west.
In particular, one evolving supercell is interacting with a remnant
outflow boundary in parts of Lee, La Salle, and Bureau Counties IL.
Given an estimated south-southeastward storm motion (per nearby
VWP), this storm could maintain residence time along the immediate
warm side of the boundary and pose an increased risk of damaging
winds, large hail, and possibly a tornado in the near term.

Farther west, additional thunderstorms are intensifying in a zone of
enhanced low-level convergence closer to the frontal wave low in
northwest IL and far east-central IA. Warm/moist inflow for these
storms and 30-40 kt of 0-6 km shear (per nearby VWP data) oriented perpendicular to the zone of low-level convergence should promote an
increase in thunderstorm organization/intensity during the next few
hours. Damaging winds and large hail continue to be the main
concerns, though a tornado or two will also be possible, given some
increase in low-level shear ahead of the frontal wave during the
next few hours.

..Weinman.. 08/21/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fjg!67FfEAgqnQ0Uam9utlj71yqSQu68S1pYgQ6cn1iJRhareoRgqNibu-8JfKWMlV0zgA65CwFsc9T__ipkCoLb1sEoR-Q$ for graphic product...

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

LAT...LON 40938944 41419018 41809030 42219028 42479008 42688933
42618875 42418849 41998835 41078851 40898887 40938944

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


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