Storm Prediction Center Mesoscale Discussion 621

   Mesoscale Discussion 0621
   NWS Storm Prediction Center Norman OK
   0240 PM CDT Wed Apr 30 2025

   Areas affected...East-central Missouri into southern Illinois

   Concerning...Severe potential...Watch possible 

   Valid 301940Z - 302145Z

   Probability of Watch Issuance...40 percent

   SUMMARY...A few storms are possible along an outflow boundary. All
   severe hazards would be possible. A watch is uncertain in the short
   term, but issuance is possible this afternoon depending on
   observational trends.

   DISCUSSION...Airmass modification after earlier convection has been
   evident over the past couple of hours in central Missouri and
   southern Illinois. The primary outflow boundary is situated just
   south of St. Louis and extends into far southern Illinois and
   southern Indiana. Dewpoints south of the boundary have increased to
   upper 60s F except for parts of southeastern Missouri which has only
   recovered into the low 60s F. North of the outflow boundary, stable
   billow clouds remain. However, very near the boundary temperatures
   and dewpoints have increased and at least some MLCIN has been
   removed and convection has begun to slowly deepen.

   With 40 kts of effective shear (more favorably oriented across the
   boundary on its western half), supercells would be expected if
   storms develop. Large hail and damaging winds would be possible. A
   tornado or two would also be possible for storms interacting with
   the more backed easterly/southeasterly winds on the cooler side of
   the boundary. Being in the wake of an earlier MCV, forcing for
   ascent will be nebulous and will depend on heating/destabilization
   along the outflow. Trends will continue to be monitored. A watch is
   possible this afternoon.

   ..Wendt/Hart.. 04/30/2025

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

   ATTN...WFO...PAH...ILX...LSX...

   LAT...LON   38359140 38649151 39179104 39229055 38878972 38828868
               38808815 38618795 38168806 37928814 37538862 37558986
               38359140 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-115 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN