Storm Prediction Center Mesoscale Discussion 1762

   Mesoscale Discussion 1762
   NWS Storm Prediction Center Norman OK
   1224 PM CDT Mon Jul 27 2026

   Areas affected...northeast IL/northwest IN

   Concerning...Severe Thunderstorm Watch 520...

   Valid 271724Z - 271900Z

   The severe weather threat for Severe Thunderstorm Watch 520
   continues.

   SUMMARY...A favorable environment supporting large to very large
   hail and a tornado risk will develop across portions of northeast IL
   into northwest IN over the next 1-2 hours.

   DISCUSSION...A supercell located over northeast IL will develop
   south/southeast across the southern greater Chicago metro vicinity.
   The downstream airmass is very moist (mid/upper 70s dewpoints) and
   unstable (3000-4000 J/kg MLCAPE). Favorable vertical shear with 50+
   kt effective shear magnitudes and 0-1 SRH near 125 m2/s2 is noted
   from the KLOT VWP. Effective STP values have increased to 3-5 as
   well. This environment will continue to support supercell structures
   with a continued risk for very large hail to around 2.5 inches,
   strong wind gusts, and possibly a strong tornado over the next 1-2
   hours.

   ..Leitman.. 07/27/2026

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

   ATTN...WFO...LOT...

   LAT...LON   42018782 41528726 41138721 40998753 41038799 41228829
               41718827 41928825 42058811 42018782 

   MOST PROBABLE PEAK TORNADO INTENSITY...100-125 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN