081
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 WWW.SPC.NOAA.GOV 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
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