599
ACUS11 KWNS 172326
SWOMCD
SPC MCD 172325
ILZ000-WIZ000-IAZ000-MOZ000-180130-
MESOSCALE DISCUSSION 0484
NWS STORM PREDICTION CENTER NORMAN OK
0625 PM CDT FRI APR 17 2026
AREAS AFFECTED...NORTHWEST ILLINOIS
CONCERNING...TORNADO WATCH 129...131...
VALID 172325Z - 180130Z
THE SEVERE WEATHER THREAT FOR TORNADO WATCH 129, 131 CONTINUES.
SUMMARY...A TRANSITION TO A PREDOMINANTLY LINEAR STORM MODE IS
LIKELY UNDERWAY AND WILL RESULT IN AN UPTICK IN SEVERE WIND
POTENTIAL AS WELL AS EMBEDDED MESOVORTICIES DOWNSTREAM ACROSS
CENTRAL/NORTHERN ILLINOIS.
DISCUSSION...IMAGERY OUT OF KDVN SHOWS SIGNS OF COLD POOL
CONSOLIDATION AND EXPANSION AS CONVECTION CONTINUES TO CLUSTER AND
GROW UPSCALE, LIKELY INDICATING THE TRANSITION FROM SEMI-DISCRETE
CELLS AND CLUSTERS TO A MORE CONSOLIDATED LINEAR STORM MODE. OVER
THE NEXT COUPLE OF HOURS ONE OR MORE ORGANIZED LINES SHOULD EMERGE
ACROSS CENTRAL TO NORTH-CENTRAL IL. THIS WILL BE ACCOMPANIED BY AN
INCREASE IN SEVERE WIND POTENTIAL AS WELL AS THE POSSIBILITY OF
EMBEDDED MESOVORTICIES, ESPECIALLY GIVEN STEADILY STRENGTHENING
LOW-LEVEL FLOW/IMPROVING WIND SHEAR NOTED IN DOWNSTREAM VWPS.
LOCALIZED CORRIDORS OF ENHANCED WIND, AND PERHAPS TORNADO, POTENTIAL
ARE EXPECTED WHERE LINE-PRECEDING CONVECTION (NOTED IN WEST-CENTRAL
IL) EVENTUALLY INTERSECT THE DEVELOPING LINE, AND COULD RESULT IN
LOCALIZED SURGES ACCOMPANIED BY SWATHS OF STRONGER (POTENTIALLY
SIGNIFICANT) WINDS.
..MOORE.. 04/17/2026
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...LOT...ILX...MKX...LSX...DVN...
LAT...LON 40419175 40709132 41209087 41579060 41979046 42249042
42359025 42528902 42488881 42368866 42168867 41868873
41508878 41168882 40778894 40478917 40268950 40099007
39999048 39989091 39989136 40039167 40169180 40259182
40419175
MOST PROBABLE PEAK TORNADO INTENSITY...100-130 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
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