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Mesoscale Discussion 1657
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   Mesoscale Discussion 1657
   NWS Storm Prediction Center Norman OK
   0302 AM CDT Tue Aug 31 2021

   Areas affected...Far Southern South Dakota...Northern and Eastern
   Nebraska...Southwest Iowa...Far Northwest Missouri

   Concerning...Severe Thunderstorm Watch 479...

   Valid 310802Z - 311000Z

   The severe weather threat for Severe Thunderstorm Watch 479

   SUMMARY...An isolated severe threat is likely to continue for a few
   more hours, mainly across northern and eastern Nebraska
   southeastward into southwest Iowa and far northwest Missouri. New
   weather watch issuance is not expected beyond the 10Z expiration
   time of WW 479.

   DISCUSSION...The latest radar imagery shows a MCS extending from
   southern sections of the northern Plains southeastward into the
   lower Missouri Valley. This large area of thunderstorms is located
   along a northwest-to-southeast corridor of moderate instability. The
   RAP is estimating MLCAPE along this corridor in the 1500 to 2000
   J/kg range. Most of the instability is located above 850 mb with
   forecast soundings showing a boundary layer temperature inversion.
   In spite of this, effective shear is estimated to be in the 30 to 35
   kt range. This combined with 700-500 mb lapse rates near 7.0 C/km
   should be enough for a isolated large hail threat with the stronger
   rotating cells. An isolated wind-damage threat will also be
   possible. However, the severe threat should become more isolated
   with time over the next few hours and should be too marginal for the
   issuance of another watch after 10Z.

   ..Broyles.. 08/31/2021

   ...Please see for graphic product...


   LAT...LON   43129857 43299944 43230047 42750076 42200026 41649875
               40679736 40149647 40009545 40219460 40489414 40879407
               41659510 42219660 43129857 

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