971  
ACUS11 KWNS 250107  
SWOMCD  
SPC MCD 250106  
INZ000-ILZ000-250230-  
 
MESOSCALE DISCUSSION 1303  
NWS STORM PREDICTION CENTER NORMAN OK  
0806 PM CDT WED JUN 24 2026  
 
AREAS AFFECTED...PORTIONS OF NORTHEASTERN ILLINOIS INTO NORTHWESTERN  
INDIANA  
 
CONCERNING...SEVERE THUNDERSTORM WATCH 387...  
 
VALID 250106Z - 250230Z  
 
THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 387  
CONTINUES.  
 
SUMMARY...THE SEVERE THREAT WILL GRADUALLY DIMINISH OVER THE NEXT  
1-2 HOURS. ISOLATED LARGE HAIL, DAMAGING WIND GUSTS, AND PERHAPS A  
BRIEF TORNADO REMAIN POSSIBLE IN THE MEANTIME.  
 
DISCUSSION...SCATTERED STRONG TO SEVERE THUNDERSTORMS REMAIN ONGOING  
ACROSS PORTIONS OF NORTHEASTERN ILLINOIS AND ARE BEGINNING TO SPREAD  
INTO NORTHWESTERN INDIANA AS OF 0100 UTC. A MIXED STORM MODE OF  
SUPERCELLS AND CLUSTERS HAS PRODUCED SPORADIC LARGE HAIL AND  
DAMAGING WIND REPORTS OVER THE PAST 1-2 HOURS, AND THIS THREAT IS  
EXPECTED TO PERSIST EAST-SOUTHEASTWARD INTO FAR NORTHWESTERN  
INDIANA, WITH ISOLATED LARGE HAIL, DAMAGING WIND GUSTS, AND PERHAPS  
A BRIEF TORNADO REMAINING POSSIBLE. OBJECTIVE ANALYSIS INDICATES  
THAT AVAILABLE BUOYANCY DECREASES RAPIDLY WITH EASTWARD EXTENT,  
HOWEVER. COUPLED WITH THE ONSET OF LOW-LEVEL NOCTURNAL  
COOLING/STABILIZATION AND THE EASTWARD PROGRESSION OF THE ATTENDANT  
MID-LEVEL SHORTWAVE TROUGH, THIS WILL RESULT IN A GRADUALLY  
DIMINISHING SEVERE THREAT OVER THE NEXT COUPLE OF HOURS. A LOCAL  
WATCH EXTENSION COULD BE NEEDED SHOULD A STRONGER STORM OR TWO  
PERSIST THROUGH THE EXPIRATION TIME OF SEVERE THUNDERSTORM WATCH 387  
AT 0300 UTC, BUT ADDITIONAL WATCH ISSUANCE IS NOT ANTICIPATED AT  
THIS TIME.  
 
..CHALMERS.. 06/25/2026  
   
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT  
 
ATTN...WFO...IWX...LOT...DVN...  
 
LAT...LON 42278925 42438890 42418821 42168719 41788692 41298688  
40878710 40708750 40778834 41138912 41808957 42098950  
42278925  
 
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH  
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH  
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN  
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