ACUS11 KWNS 172326
SWOMCD
SPC MCD 172325=20
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 https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!8hXBhF0byiS-Nuqa_dJ6T0CdYrrlBLq2HvdPWjP0dgUDAlI43_NUhUCsyqDuDnLA7cnMhwXpI= iULnTWDZNftFHdUxbU$ 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=20

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


=3D =3D =3D
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