Mesoscale Discussion 1461
   NWS Storm Prediction Center Norman OK
   0112 PM CDT Tue Aug 10 2021

   Areas affected...Portions of south-central and eastern Iowa

   Concerning...Severe potential...Watch possible 

   Valid 101812Z - 101945Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Monitoring storm intensity/coverage across eastern Iowa
   for a potential severe thunderstorm watch.

   DISCUSSION...A storm has formed in Clarke County, Iowa. SPC
   mesoanalysis and forecast soundings would suggest a bit more warming
   would have been expected before widespread surface based storm
   development was imminent. However, radar characteristics suggest
   this storm could be surface based. Therefore, more widespread
   surface based storm development may be more imminent than previously
   thought. Instability across eastern Iowa is extreme with MLCAPE
   around 4000 J/kg and mid-level lapse rates around 8 C/km per SPC
   mesoanalysis. 

   Based on the DMX and EAX VWPs there appears to be some stronger
   mid-level flow across southern Iowa which may provide enough shear
   for some better storm organization.

   Therefore, given the extreme instability and at least modest shear,
   any sustained, organized convection will likely be severe. The
   primary question at this time will be storm coverage. Therefore,
   storm trends will continue to be monitored and if/when stronger,
   sustained updrafts appear imminent, a watch may become necessary.

   ..Bentley/Thompson.. 08/10/2021

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

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

   LAT...LON   40689447 41899378 42999273 42919114 42509083 41339121
               40709169 40689447