Storm Prediction Center Mesoscale Discussion 1670

   Mesoscale Discussion 1670
   NWS Storm Prediction Center Norman OK
   0755 AM CDT Mon Jul 20 2026

   Areas affected...Far Southeast Minnesota...Eastern Iowa

   Concerning...Severe potential...Watch unlikely 

   Valid 201255Z - 201500Z

   Probability of Watch Issuance...20 percent

   SUMMARY...An isolated wind-damage threat will likely continue with a
   short line of strong to severe storms near the Iowa-Minnesota state
   line. This line will move south-southeastward across eastern Iowa
   over the next couple of hours. The threat is expected to be marginal
   and weather watch issuance appears unlikely.

   DISCUSSION...The latest surface analysis shows a north-to-south
   corridor of low-level moisture from far western Missouri northward
   into western Iowa, along which dewpoints are in the mid 70s F.
   Slightly further east, the RAP has an axis of moderate instability
   with MLCAPE in the 1000 to 2000 J/kg range analyzed over central
   Iowa. Scattered thunderstorms are ongoing along the instability
   gradient to the east of this axis. The storms are being supported by
   a subtle mid-level shortwave trough evident on water vapor imagery
   moving southeastward across the upper Mississippi Valley. Although
   forecast soundings across eastern Iowa this morning have a
   near-surface inversion in place, effective shear is estimated to be
   near 40 knots. This could support an isolated and marginal threat
   for severe wind gusts over the next couple of hours, especially as
   surface temperatures ahead of the storms begin to increase.

   ..Broyles/Smith.. 07/20/2026

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

   ATTN...WFO...DVN...ARX...MPX...DMX...

   LAT...LON   43549372 43049385 41999340 41419293 41159252 41039199
               41089155 41329112 41759080 42189082 42839106 43439143
               43809184 43999228 43979296 43799344 43549372 

   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN