ACUS11 KWNS 180109
SWOMCD
SPC MCD 180109=20
INZ000-MIZ000-ILZ000-WIZ000-180315-

Mesoscale Discussion 0485
NWS Storm Prediction Center Norman OK
0809 PM CDT Fri Apr 17 2026

Areas affected...Central Illinois into northwest Indiana

Concerning...Tornado Watch 131...

Valid 180109Z - 180315Z

The severe weather threat for Tornado Watch 131 continues.

SUMMARY...A line of severe thunderstorms will continue to push
east/southeast over the next few hours and will continue to pose a
risk of severe wind and embedded circulations.

DISCUSSION...A consolidated line of severe thunderstorms is now
evident in MRMS imagery with several embedded surges noted across
western and northwest IL. KILX radar velocity data shows swaths of
higher winds within the surging segments with several gusts between
45-65 mph noted over the past 30 minutes along the line. Downstream,
low-level winds continue to strengthen across central IL. The KILX
VWP sampling winds between 50-55 knots below 1 km, and a recent 00z
ILX RAOB sampled MLCAPE upwards of 1600 J/kg with 50 knots of
effective bulk shear and around 200 m2/s2 effective SRH.
Consequently, the downstream environment remains favorable for
maintenance of the severe line as it continues east/southeast over
the next few hours across IL. While the primary threat will remain
swaths of severe winds (most likely between 60-70 mph, but possibly
as high as 75 mph), favorable bulk shear values from the surface
through 3 km will continue to favor the development of embedded
circulations within the line.=20

Eastward expansion of WW 131 will likely be needed in the coming
hours across portions of eastern IL. Drier low-level conditions
downstream across IN casts some uncertainty on how intense the line
will be beyond roughly the 05-06 UTC time frame into IN, but
convective trends will be monitored for the need for downstream
watch issuance.

..Moore.. 04/18/2026

...Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj= g!9XNa3oP6WSoAFVPPilEMfUEBNx1gOK9UyqgNXbCV5UFrQrR6I6OfozYWu0z5iANVAJkz4SpYu= fJ5-OthnoUUp4Aeuco$ for graphic product...

ATTN...WFO...IWX...IND...LOT...ILX...MKX...LSX...DVN...

LAT...LON 39188775 39108832 39138888 39369064 39459087 39589096
39739100 39859069 40039036 40448997 41038952 41568919
42008896 42328872 42488847 42608799 42498768 41928747
41798734 41788704 41888679 41748656 41278645 40788660
39778708 39418753 39188775=20

MOST PROBABLE PEAK TORNADO INTENSITY...100-130 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


=3D =3D =3D
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