Mesoscale Discussion 0488
   NWS Storm Prediction Center Norman OK
   1019 PM CDT Fri Apr 17 2026

   Areas affected...Eastern Illinois into western Indiana

   Concerning...Tornado Watch 131...133...

   Valid 180319Z - 180515Z

   The severe weather threat for Tornado Watch 131, 133 continues.

   SUMMARY...Severe winds and QLCS tornadoes will remain possible for
   the next couple of hours across eastern Illinois and into western
   Indiana. However, the early stages of a weakening trend are noted,
   suggesting that the severe threat should gradually wane with time.

   DISCUSSION...Over the past hour, several severe wind reports have
   been noted with an organized squall line as it moved across central
   IL. However, the early stages of a weakening trend are noted with
   the line across several metrics, including MRMS VIL, GOES IR
   cloud-top temperatures, and lightning counts. This weakening has
   been anticipated by recent high-res guidance during the 04-06 UTC
   period as the line migrates out of the primary buoyancy axis and
   into a drier air mass located downstream across central IN. The
   noted convective trends seem to be affirming these short-term
   forecasts, so further weakening appears likely as the line continues
   east. However, VWP observations downstream at KIND show an uptick in
   low-level wind shear with 0-1 km SRH recently increasing to around
   550 m2/s2. This highly favorable low-level wind environment will
   continue to support the potential for severe winds and embedded QLCS
   tornadoes within the line at least for the next couple of hours as
   it crosses into western IN. How long this threat will persist
   downstream remains somewhat unclear given the ongoing weakening
   trend.

   ..Moore.. 04/18/2026

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...IWX...IND...LOT...ILX...

   LAT...LON   39648873 40008822 40568796 41058788 41308788 41618782
               41788763 41798743 41788716 41838695 41918677 41868585
               41718569 41418570 40958589 40518615 39948655 39508699
               39428736 39418797 39518854 39648873 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN