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Mesoscale Discussion 1725
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   MESOSCALE DISCUSSION 1725
   NWS STORM PREDICTION CENTER NORMAN OK
   0245 PM CDT THU AUG 20 2015

   AREAS AFFECTED...PORTIONS OF NY SWD TO NRN VA

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 201945Z - 202215Z

   PROBABILITY OF WATCH ISSUANCE...5 PERCENT

   SUMMARY...SHOWERS AND SCATTERED THUNDERSTORMS CROSSING THE REGION
   THIS AFTERNOON WILL HAVE THE POTENTIAL TO PRODUCE LOCALLY GUSTY
   WINDS. A FEW SPORADIC INSTANCES OF LOCALLY DMGG WIND GUSTS MAY
   OCCUR...THOUGH WW ISSUANCE IS NOT ANTICIPATED.

   DISCUSSION...CONVECTION HAS ORGANIZED ALONG A LINE EXTENDING FROM
   NEAR ROCHESTER NY TO HAGERSTOWN MD NEAR/AHEAD OF A COLD FRONT
   ADVANCING EWD...WITH EMBEDDED SCATTERED THUNDERSTORMS BASED ON
   CG-LIGHTNING DATA. DESPITE POOR MID-LEVEL LAPSE RATES AHEAD OF THIS
   ACTIVITY...POCKETS OF SFC HEATING AMIDST SFC DEWPOINTS IN THE UPPER
   60S TO LOWER 70S ARE SUPPORTING MLCAPE AROUND 500-1000 J/KG. THIS
   BUOYANCY IS BEING STUNTED ACROSS PARTS OF CNTRL/ERN PA AND ADJACENT
   NY WHERE EARLIER PRE-FRONTAL-CONFLUENCE-RELATED CONVECTION PROCESSED
   HIGHER-THETA-E AIR EARLIER IN THE DAY. 

   REGARDLESS...THE AFOREMENTIONED QUASI-LINEAR CONVECTION SHOULD
   CONTINUE TO SPREAD EWD OVER THE NEXT FEW HOURS -- DURING PEAK
   HEATING. CROSS-FRONTAL TEMPORAL-PRESSURE-TENDENCY GRADIENTS ARE
   MINIMAL...SUGGESTING THAT BACKGROUND ISALLOBARIC-FLOW ENHANCEMENTS
   TO CONVECTIVE-WIND POTENTIAL ARE MINIMAL. REGARDLESS...AREA VWPS ARE
   SAMPLING AROUND 20-30 KT OF DEEP SHEAR THAT MAY MAINTAIN ORGANIZED
   CONVECTIVE STRUCTURES...WITH CONVECTIVE MOMENTUM TRANSPORT
   POTENTIALLY ENCOURAGING A FEW STRONG SFC WIND GUSTS IN SMALL-SCALE
   BOWS/LEWP SEGMENTS/WEAK MESO-VORTICES.

   HOWEVER...GIVEN THE PAUCITY OF NORMALIZED CAPE...THE DEARTH OF DEEP
   UPWARD MOTION GIVEN THE NNWWD DISPLACEMENT OF LARGER-SCALE-
   CYCLONE-RELATED DCVA RELATIVE TO THE LOCAL AREA...AND PROVIDED THE
   LACK OF EVEN STRONGER LOW/MID-LEVEL FLOW...WIND GUSTS EXCEEDING 50
   KT ARE HIGHLY UNLIKELY. REGARDLESS...THE AFOREMENTIONED PARAMETERS
   WILL BE SUFFICIENT...AMIDST 1.75-2.10-INCH PW ENHANCING
   WATER-LOADING PROCESSES IN DOWNDRAFTS...FOR A FEW SPORADIC INSTANCES
   OF LOCALIZED TREE DAMAGE AND/OR DAMAGE TO POWER LINES. AREAS ACROSS
   THE MID-ATLANTIC WHERE LOW-LEVEL LAPSE RATES ARE RELATIVELY STEEPER
   OWING TO MORE ABUNDANT INSOLATION MAY BE THE PRIMARY FOCUS FOR SUCH
   ACTIVITY.

   ..COHEN/KERR.. 08/20/2015


   ATTN...WFO...BTV...PHI...BGM...AKQ...BUF...CTP...LWX...

   LAT...LON   43927677 44637550 43837551 39897599 38597634 38147749
               39197817 42877747 43927677 

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Page last modified: August 20, 2015
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