Storm Prediction Center Mesoscale Discussion 1156

   Mesoscale Discussion 1156
   NWS Storm Prediction Center Norman OK
   0450 PM CDT Tue Jun 16 2026

   Areas affected...central IL into west-central and north-central IN

   Concerning...Severe Thunderstorm Watch 338...

   Valid 162150Z - 162315Z

   The severe weather threat for Severe Thunderstorm Watch 338
   continues.

   SUMMARY...Several supercells will potentially be capable of a threat
   for mainly large hail (1 to 1.75 inches in diameter).  Localized
   severe gusts (55-65 mph) are possible with the stronger cores.  A
   brief tornado is also possible.

   DISCUSSION...Water-vapor imagery shows a potent upper shortwave
   trough moving east across the central Great Lakes.  Surface analysis
   places a cold front from the mid MS Valley arching
   east-northeastward into east-central IL and northeastward into the
   southern Lake Michigan vicinity.  This boundary is serving as the
   primary low-level forcing mechanism for storm development late this
   afternoon from central IL northeastward towards Lafayette, IN. 
   Ahead of these storms---which contain a few supercell left-right
   splits---surface conditions of lower 70s deg F temperatures and mid
   50s dewpoints are observed. 

   RAP forecast soundings show cold 500-mb temperatures (-16 to -18 deg
   C) and gradually veering and strengthening flow with height beneath
   80-kt 300 mb westerly flow.  As a result, sufficient buoyancy/shear
   will continue to support supercells for the next several hours. 
   Large hail appears to be the primary severe hazard, but localized
   severe gusts and perhaps a brief tornado are also possible.

   ..Smith.. 06/16/2026

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

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

   LAT...LON   40268572 39618691 39368841 39438886 39638888 39788878
               39888806 40098748 40568702 41018674 41158592 41018550
               40778538 40268572 

   MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN