Storm Prediction Center Mesoscale Discussion 1310

   Mesoscale Discussion 1310
   NWS Storm Prediction Center Norman OK
   0111 PM CDT Thu Jun 25 2026

   Areas affected...Eastern Missouri into southern Illinois and
   southwest Indiana

   Concerning...Severe potential...Watch unlikely 

   Valid 251811Z - 252015Z

   Probability of Watch Issuance...20 percent

   SUMMARY...Scattered thunderstorms will continue to develop through
   late afternoon. Sporadic instances of large hail and damaging winds
   appear possible, but will most likely remain too isolated to warrant
   watch issuance.

   DISCUSSION...Over the past hour, thunderstorms have been slowly
   deepening in the St. Louis area and eastward into southern IL. This
   activity appears to be driven primarily by a combination of weak
   low-level confluence and glancing ascent from a passing upper-level
   wave to the north across central/northern IL. Despite the weak
   ascent, very moist low-level conditions coupled with continued
   diurnal warming are quickly eroding any lingering MLCIN and should
   result in scattered to somewhat widespread thunderstorm coverage
   from eastern MO to southwest IN over the next several hours. The
   moist low-level conditions are also compensating for the otherwise
   limited mid-level lapse rates and supporting MLCAPE values on the
   order of 2000 J/kg. Recent VWP observations from KLSX are sampling
   0-6 km bulk wind values on the order of 20-25 knots, which aligns
   well with recent RRFS solutions and suggests some storm organization
   is possible, including the potential for transient supercell
   structures across southern IL where deep-layer wind shear should be
   slightly stronger. However, weak low-level winds will likely promote
   outflow-dominant convection that may modulate storm lifespans and
   favor clustered storm modes. Nonetheless, sporadic instances of
   large hail (possibly as high as 1.5 inches) and damaging winds
   appear possible through late afternoon based on the convective
   environment and output from the past few RRFS solutions.

   ..Moore/Guyer.. 06/25/2026

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

   ATTN...WFO...LMK...IND...PAH...ILX...LSX...

   LAT...LON   39069079 39218752 39228683 38958657 38688655 38368674
               38078709 37948743 37788835 37768971 37859051 38109087
               38399105 38849111 39069079 

   MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN