Storm Prediction Center Mesoscale Discussion 466

   Mesoscale Discussion 0466
   NWS Storm Prediction Center Norman OK
   0505 AM CDT Fri Apr 18 2025

   Areas affected...Northeast Iowa...Southern Wisconsin

   Concerning...Severe potential...Watch unlikely 

   Valid 181005Z - 181230Z

   Probability of Watch Issuance...20 percent

   SUMMARY...An isolated threat for large hail and severe gusts will
   likely continue across parts of northeast Iowa over the next few
   hours. The threat is also expected to affect parts of southern
   Wisconsin. Weather watch issuance is unlikely.

   DISCUSSION...The latest high-resolution radar imagery from Des
   Moines shows a cluster of thunderstorms across northeast Iowa and
   far southwest Wisconsin. Some of these storms have produced severe
   reports over the last couple of hours. The cluster will continue to
   move eastward into southern Wisconsin this morning. RAP forecast
   soundings from northeast Iowa into southern Wisconsin have a
   temperature inversion up to about 850 mb. Across northeast Iowa,
   MUCAPE is estimated by the RAP in the 1000 to 2000 J/kg range.
   Instability further to the east is considerably less, but an
   increase in instability could still occur as warm advection
   continues through the morning. In addition, RAP analysis across
   northeast Iowa has effective shear generally in the 40 to 50 knot
   range. This environment should support elevated supercells capable
   of producing isolated large hail. In spite of the low-level
   temperature inversion, a strong to severe gust will also be
   possible. The severe threat should develop eastward across southern
   Wisconsin but may become more isolated as the storms outrun the
   instability further to the west.

   ..Broyles/Gleason.. 04/18/2025

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

   ATTN...WFO...LOT...MKX...DVN...ARX...DMX...

   LAT...LON   42458882 42479059 42539253 42669327 43109340 43499266
               43488999 43368824 42768793 42508828 42458882 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN