Storm Prediction Center Mesoscale Discussion 1674

   Mesoscale Discussion 1674
   NWS Storm Prediction Center Norman OK
   0153 PM CDT Mon Jul 20 2026

   Areas affected...Northeast Iowa into northwest/north-central
   Wisconsin

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

   Valid 201853Z - 202100Z

   Probability of Watch Issuance...95 percent

   SUMMARY...All severe hazards, including some significant, are
   possible as supercells develop by late afternoon. Timing and
   location of initiation are the main uncertainties. A tornado watch
   is likely.

   DISCUSSION...A very moist airmass is evident ahead of a cold front
   in the Upper Mississippi Valley. A capping inversion was present on
   the 12Z MPX observed sounding. Cumulus along the front have yet to
   become vertically developed as a result. Mid-level convection has
   been ongoing in southern Minnesota. This activity is now moving into
   modifying outflow from an earlier MCS in the La Crosse/Davenport
   vicinity. Lift from a shortwave trough in northern Minnesota will
   continue to overspread the area this afternoon. With time, continued
   heating and moistening ahead of the cold front and near the outflow
   front intersection should allow storms to develop, most likely by
   late afternoon. Given strong shear (50-60 kt effective) across the
   cold front, supercell structures will be favored. Steep mid-level
   lapse rates will support the threat for large to very-large hail. A
   tornado threat, some possibly strong, will also be present with
   supercells. Severe winds will also be possible. Wind gusts of 75+
   mph are possible, particularly where activity grows upscale. The
   exact timing/location of storm initiation is not clear though a
   tornado watch is likely.

   ..Wendt/Thompson.. 07/20/2026

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

   ATTN...WFO...MQT...GRB...MKX...DLH...ARX...MPX...

   LAT...LON   43609277 44549244 46519079 46729022 46408897 45168894
               43798985 43379033 43099126 43079238 43609277 

   MOST PROBABLE PEAK TORNADO INTENSITY...120-145 MPH
   MOST PROBABLE PEAK WIND GUST...65-80 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN