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Mesoscale Discussion 1479
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   Mesoscale Discussion 1479
   NWS Storm Prediction Center Norman OK
   1201 PM CDT Wed Aug 11 2021

   Areas affected...Far eastern West Virginia...northern and central
   Virginia...and portions of Maryland.

   Concerning...Severe potential...Watch possible 

   Valid 111701Z - 111830Z

   Probability of Watch Issuance...60 percent

   SUMMARY...Storms are expected to move off the higher terrain of the
   Appalachians and pose a threat for damaging wind gusts this
   afternoon/evening.

   DISCUSSION...Convective initiation has begun in the higher terrain
   in Randolph and Pendleton Counties and vicinity. The airmass is
   still capped in the lower elevations according to SPC Mesoanalysis,
   but with rapid surface heating, expect the remaining inhibition to
   be eroded within the next hour. Visible satellite gives further
   support for this as cumulus have started to form in the lower
   elevations across northern Virginia. The 12Z LWX RAOB showed
   moderately steep mid-level lapse rates (~7 C/km) but very weak
   effective shear (6 kts). These steep mid level lapse rates combined
   with temperatures in the low 90s and dewpoints in the upper 60s has
   combined for MLCAPE around 2000 J/kg per SPC mesoanalysis. Some
   additional heating may bring greater instability and MLCAPE around
   2500 J/kg within the next hour. In addition, the airmass will be
   very supportive for strong downdrafts with DCAPE already around 1200
   J/kg. 

   Storm organization is not anticipated given the shear profile is not
   forecast to improve much from the LWX 12Z RAOB. However, the
   favorable thermodynamic environment and storm density, which should
   lead to clustering, should be sufficient for a damaging wind threat.


   A watch may be needed in the next 1 to 2 hours.

   ..Bentley/Thompson.. 08/11/2021

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

   ATTN...WFO...AKQ...LWX...RNK...PBZ...RLX...

   LAT...LON   38657994 39327924 39687826 39707725 39517665 38617656
               37657686 37087780 36997884 37147975 37678024 38657994 

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