Storm Prediction Center Mesoscale Discussion 873

   Mesoscale Discussion 0873
   NWS Storm Prediction Center Norman OK
   0115 PM CDT Tue May 21 2024

   Areas affected...Southern WI

   Concerning...Severe potential...Watch possible 

   Valid 211815Z - 211945Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Isolated hail and/or damaging gusts are possible. Limited
   severe coverage will likely preclude the need for a watch in the
   short term. A greater severe risk is anticipated later this evening
   as the line of storms moving out of IA moves into the region.

   DISCUSSION...Surface observations reveal a warm front extends
   east-to-west across far southern WI, with temperatures in the upper
   70s/low 80s south of the boundary and in the mid 60s to low 70s
   north of it. Dewpoints south of the boundary are in the upper 60s
   while remaining in the low to mid 60s north of it. Ongoing
   convective cluster moving across southwest WI has recently shown a
   strengthening trend, likely a result of increased warm-air advection
   across the warm front. Given the persistence of the strong low-level
   flow and increasing low-level moisture, this cluster is forecast to
   continue quickly northeastward, with some potential for isolated
   hail and/or damaging gusts as it does. 

   A more isolated storm has developed east of this cluster in Dane
   County. This storm is very close to the warm front but still looks
   to be slightly elevated, although the more recent slow, more
   eastward storm motion may be indicating a trend toward more
   surface-based character. Recent MKX VAD sampled enough low-level
   curvature to support some tornado potential if the storm can become
   surface-based. Otherwise, the primary risk with this storm is large
   hail.

   Limited severe coverage will likely preclude the need for a watch,
   but convective trends are being monitored closely. A greater severe
   risk is anticipated later this evening as the line of storms moving
   out of IA moves into the region.

   ..Mosier/Guyer.. 05/21/2024

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

   ATTN...WFO...GRB...MKX...ARX...

   LAT...LON   42718888 42989012 44149022 44618904 44148788 43108817
               42718888