969
ACUS11 KWNS 172143
SWOMCD
SPC MCD 172142
ILZ000-WIZ000-172345-
MESOSCALE DISCUSSION 0480
NWS STORM PREDICTION CENTER NORMAN OK
0442 PM CDT FRI APR 17 2026
AREAS AFFECTED...SOUTHERN WISCONSIN AND FAR NORTHERN ILLINOIS
CONCERNING...TORNADO WATCH 129...131...
VALID 172142Z - 172345Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 129, 131 CONTINUES.
SUMMARY...LEADING SUPERCELLS ACROSS NORTHERN ILLINOIS AND SOUTHERN
WISCONSIN WILL LIKELY POSE A TORNADO (POSSIBLY SIGNIFICANT) AND VERY
LARGE HAIL THREAT AS THEY MOVE DOWNSTREAM OVER THE NEXT 1-2 HOURS.
DISCUSSION...A PAIR OF LEADING SUPERCELLS CONTINUES TO PRECEDE A
BROKEN LINE OF STORMS ALONG THE IL/WI BORDER. REGIONAL RADAR IMAGERY
CONTINUES TO INDICATE THAT THESE CELLS ARE RATHER INTENSE WITH A
THREE-BODY SCATTER SPIKE, A BOUNDED WEAK ECHO REGION, AND A RECENT
3-INCH HAIL REPORT NOTED WITH THE SOUTHERN STORM. AN IMPROVING
DOWNSTREAM CONVECTIVE ENVIRONMENT IS NOTED IN RECENT OBSERVATIONS
AND ANALYSES (0-1 KM SRH VALUES REMAIN BETWEEN 200-250 M2/S2 PER THE
KMKX VWP, AND STP VALUES HAVE RECENTLY INCREASED TO 2-3 PER RECENT
MESOANALYSIS). ADDITIONALLY, THE SOUTHERN STORM WILL ALSO LIKELY
PROPAGATE ALONG A SUBTLE SURFACE THETA-E GRADIENT DRAPED ACROSS
NORTHERN IL TO SOUTHERN WI. GIVEN THESE TRENDS AND THE PRESENCE OF A
WELL-ESTABLISHED UPDRAFT/MESOCYCLONE WITH THE SOUTHERN CELL, THE
POTENTIAL FOR VERY LARGE HAIL (LIKELY IN EXCESS OF 2 INCHES) AND
STRONG TORNADOES WILL LIKELY PERSIST FOR THE NEXT COUPLE OF HOURS
DOWNSTREAM INTO SOUTHEAST WI AND FAR NORTHERN IL.
..MOORE.. 04/17/2026
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...LOT...MKX...DVN...
LAT...LON 42138771 42158906 42268948 42378957 42608965 42798955
42968903 43188791 43108770 42848764 42588767 42138771
MOST PROBABLE PEAK TORNADO INTENSITY...140-170 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...2.75-4.25 IN
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