Storm Prediction Center Mesoscale Discussion 791

   Mesoscale Discussion 0791
   NWS Storm Prediction Center Norman OK
   0214 PM CDT Thu May 15 2025

   Areas affected...Parts of southern Wisconsin into northern Illinois

   Concerning...Severe potential...Tornado Watch likely 

   Valid 151914Z - 152115Z

   Probability of Watch Issuance...80 percent

   SUMMARY...A tornado watch will likely be needed this afternoon.
   Supercells capable of all severe hazards are expected within the
   next few hours.

   DISCUSSION...Cumulus continue to deepen both along a dryline and an
   area of confluence within the Mississippi Valley. Whether storms
   develop within the confluence or when the dryline reaches the
   Mississippi River remains a question. 40-50 kts of effective shear
   across these surface convergence zones will favor supercells as
   storms develop. Large to very large hail will be a concern as well
   as severe wind gusts. The 18Z DVN sounding sampled very steep
   mid-level lapse rates and a long hodograph. Tornado potential will
   also be present. Surface temperature/dewpoint spreads are near 20 F,
   but low-level shear and a supercellular mode will favor low-level
   rotation. The time frame of greater tornado potential will likely be
   22-00Z when the low-level jet increases in southern Wisconsin.

   ..Wendt/Mosier.. 05/15/2025

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

   ATTN...WFO...GRB...LOT...MKX...DVN...ARX...

   LAT...LON   41418999 41579025 41819042 42309082 42909119 43299134
               43549126 44009048 44358993 44438931 43978880 43168862
               42128827 41798867 41418999 

   MOST PROBABLE PEAK TORNADO INTENSITY...120-150 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN