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Mesoscale Discussion 1797
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   Mesoscale Discussion 1797
   NWS Storm Prediction Center Norman OK
   0841 PM CDT Sun Sep 18 2022

   Areas affected...much of southern Iowa into far northern Missouri
   and northwest Illinois

   Concerning...Tornado Watch 536...

   Valid 190141Z - 190445Z

   The severe weather threat for Tornado Watch 536 continues.

   SUMMARY...A gradual ramp up in storm intensity and coverage remains
   possible over the next few hours. An additional watch could be
   needed downstream into Illinois, dependent on trends.

   DISCUSSION...A few strong storms currently exist in a weak warm
   advection zone over eastern IA into northwest IL, with more robust
   development now noted along the IA/MO border. Surface analysis shows
   little surface convergence and in face very weak wind speeds. Just
   off the surface, 850 winds are gradually increasing out of the
   west/southwest, with glancing theta-e advection into the region.

   The best deep-layer theta-e appears to exist from southern IA into
   northern MO per objective analysis, and any storms that develop in
   these areas may have the greatest potential to eventually become
   severe. Long hodographs will favor large hail, with severe wind
   threat dependent on how many storms can form with merging outflows.
   If this occurs, another watch may be required eastward into IL.

   ..Jewell.. 09/19/2022

   ...Please see for graphic product...


   LAT...LON   40589451 40909485 41539446 41979133 41759033 41058946
               40338921 39878962 39789075 39959234 39959234 40589451 

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