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Mesoscale Discussion 1390
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MD 1390 graphic

   Mesoscale Discussion 1390
   NWS Storm Prediction Center Norman OK
   0219 PM CDT Thu Jul 29 2021

   Areas affected...Parts of southeastern Iowa...northeastern
   Missouri...central Illinois and Indiana

   Concerning...Severe potential...Watch possible 

   Valid 291919Z - 292115Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Scattered strengthening thunderstorm development through
   5-7 PM CDT may gradually pose increasing risk for locally damaging
   wind gusts.  The potential for activity to consolidate into a larger
   cluster that would require a severe weather watch remains uncertain,
   and appears relatively low, but trends are being monitored for this

   DISCUSSION...Forcing for ascent along a stalled outflow boundary has
   remained sufficient to maintain sustained modest thunderstorm
   development along a corridor near the Burlington, IA through Peoria,
   IL vicinities.  Associated outflow and anvil cloud cover and light
   precipitation continue to impact the environment to the southeast of
   this activity, but the influence may be waning with a corridor of
   recent stronger surface pressure falls evident in observations
   across the Springfield and Mattoon, IL vicinities.  Additionally,
   scattered new thunderstorm development is underway in closer
   proximity to the outflow boundary, near/north of the Interstate 74
   corridor, into central Indiana.

   The newer thunderstorm development coincides with a corridor
   seasonably high precipitable water on the order of 2 inches, in the
   presence of modest shear beneath 20-40 kt northwesterly flow around
   the 500 mb level.  Gradually, with increasing inflow of a very moist
   boundary layer characterized by mid/upper 70s surface dew points,
   and large CAPE growing in excess of 3000-4000 J/kg with increasing
   insolation, substantive further intensification appears probable
   through 22-00Z.  This may include the evolution of isolated
   supercells and small organizing clusters, with at least modestly
   steep lower/mid tropospheric lapse rates and heavy precipitation
   loading contributing to the risk for potentially damaging wind

   ..Kerr/Hart.. 07/29/2021

   ...Please see for graphic product...


   LAT...LON   40809250 40869094 40858985 40788911 40548762 39848493
               38838683 39058987 39789180 40809250 

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