Mesoscale Discussion 1770
   NWS Storm Prediction Center Norman OK
   0355 PM CDT Mon Sep 20 2021

   Areas affected...portions of central into eastern Iowa...far
   southeast Minnesota...western into northern Wisconsin

   Concerning...Severe Thunderstorm Watch 507...

   Valid 202055Z - 202230Z

   The severe weather threat for Severe Thunderstorm Watch 507
   continues.

   SUMMARY...The severe threat continues with Severe Thunderstorm Watch
   507, and should persist through the afternoon. Damaging gusts and
   occasional large hail are expected to remain the primary threats,
   though a brief tornado cannot be completely ruled out. A new WW may
   be needed to the northeast of Severe Thunderstorm Watch 507.

   DISCUSSION...Temperatures have reached or exceeded 80F across much
   of the warm sector ahead of the ongoing line of storms, south of a
   warm front draped across northern WI, contributing up to 1500 J/kg
   MLCAPE in spots. Storms along/ahead of the eastward advancing cold
   front have obtained predominantly linear structures, posing a threat
   for mainly damaging gusts, though a couple instances of marginally
   severe hail remain possible, especially across northern portions of
   Severe Thunderstorm Watch 507 given 45+ kts of effective bulk shear
   in place.

   While the tornado threat is expected to remain limited overall, over
   200 m2/s2 of effective SRH has been noted in proximity to the warm
   front by the 20Z mesoanalysis, with the 2024Z ARX VWP showing well
   over 200 m2/s2 SRH within the 0-1 km layer alone. Despite the linear
   storm mode, any segment which can become more northwest-southeast
   aligned (oriented relatively more normal to the 45+ kt effective
   bulk shear vector) would support some potential for a brief tornado
   given adequate buoyancy.

   ..Squitieri/Hart.. 09/20/2021

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

   ATTN...WFO...MQT...GRB...DVN...DLH...ARX...MPX...DMX...

   LAT...LON   40629466 42649403 44469346 45559311 46119259 46489176
               46509074 46318999 45898955 44719025 42379077 40859166
               40619188 40629466