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Mesoscale Discussion 817
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   Mesoscale Discussion 0817
   NWS Storm Prediction Center Norman OK
   0234 PM CDT Tue May 23 2017

   Areas affected...Portions of central TX

   Concerning...Severe potential...Watch possible 

   Valid 231934Z - 232130Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Some increase in severe potential should occur over the
   next several hours, with isolated large hail and damaging winds the
   main threats. Watch issuance is possible.

   DISCUSSION...19Z surface analysis shows a cold front extending from
   northeast to central TX, continuing into west TX. Surface pressure
   falls of 2-4 mb per 2 hours across central TX ahead of the front
   suggest large-scale ascent attendant to a southeastward-moving
   shortwave trough over the southern High Plains is overspreading the
   discussion area. Some elevated convection has recently developed
   behind the front, likely associated with the shortwave trough. As
   these thunderstorms move quickly east-southeastward, they will have
   some potential to become surface based. Clearing ahead of the front
   has allowed for diurnal heating to destabilize the airmass across
   the warm sector of central TX. Latest RAP Mesoanalysis indicates
   MLCAPE of 500-1000 J/kg has developed this afternoon. Further
   heating may allow MLCAPE values to approach 1500 J/kg through the
   peak of the diurnal heating cycle.

   Northwesterly low-level winds strengthen with height, supporting
   effective bulk shear values of 45-50 kt. Convective coverage and
   evolution remains somewhat unclear this afternoon across central TX
   and vicinity. But, consensus of short-term guidance points to an
   increasing potential for supercell development over the next several
   hours along and ahead of the front, with large hail and damaging
   winds both possible. Depending on convective trends this afternoon,
   watch issuance is possible.

   ..Gleason/Kerr.. 05/23/2017

   ...Please see for graphic product...


   LAT...LON   29599956 30709929 31279856 31709780 31829680 31549582
               31009581 30139630 29629679 29389749 29189832 29239915

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