Storm Prediction Center Mesoscale Discussion 1764

   Mesoscale Discussion 1764
   NWS Storm Prediction Center Norman OK
   0108 PM CDT Mon Jul 27 2026

   Areas affected...portions of far eastern IL into IN

   Concerning...Severe potential...Watch likely 

   Valid 271808Z - 271945Z

   Probability of Watch Issuance...95 percent

   SUMMARY...An intense bow echo is developing across northeast IL
   south of Chicago. Potential is increasing for a swath of
   severe/damaging gusts to develop southeast across parts of far
   eastern IL into northern/central IN through early evening. A new
   watch is likely downstream from WW 520.

   DISCUSSION...A supercell over northeast IL is transitioning toward
   an intense bow. This is occurring within a corridor of
   strong/extreme instability (3000-4000 J/kg MLCAPE) and 45+ kt
   effective shear magnitudes. The downstream airmass into central IN
   will support maintenance of this developing bow as convection
   develops southeast at around 40-45 kt. KLOT radar indicates 80 kt
   winds just a few hundred feet above ground level. Given the
   favorable thermodynamic and kinematic environment downstream, a
   swath of damaging winds to 80 mph will be possible across western
   portions of WW 519 over the next hour. Convection is expected to
   continue into central IN this afternoon into early evening. In
   addition to intense/damaging wind gusts, isolated large hail and a
   tornado or two also are possible. A downstream watch will likely be
   needed soon.

   ..Leitman/Hart.. 07/27/2026

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

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

   LAT...LON   41848732 41548667 41078593 40338542 39828524 39458532
               39148563 38918604 38768645 38738688 38828748 39208783
               39888796 40658810 41218798 41518797 41738785 41848732 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN