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Mesoscale Discussion 1339
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   MESOSCALE DISCUSSION 1339
   NWS STORM PREDICTION CENTER NORMAN OK
   1159 AM CDT THU JUL 09 2015

   AREAS AFFECTED...PORTIONS OF PA/MD/WV AND FAR NORTH VA

   CONCERNING...SEVERE POTENTIAL...TORNADO WATCH LIKELY 

   VALID 091659Z - 091900Z

   PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   SUMMARY...A TORNADO WATCH WILL LIKELY BE NEEDED FOR AN INCREASING
   DAMAGING WIND/ISOLATED TORNADO RISK BY MID/LATE AFTERNOON
   PARTICULARLY ACROSS CENTRAL/EASTERN PORTIONS OF PA/MD/WV AND
   ADJACENT FAR NORTHERN VA.

   DISCUSSION...A SURFACE LOW CONTINUES TO SHIFT EASTWARD ACROSS LAKE
   ERIE VICINITY TOWARD NORTHERN PA EARLY THIS AFTERNOON...WHILE A
   PRECEDING WARM FRONT WILL CONTINUE TO GRADUALLY SPREAD NORTHWARD
   ACROSS PA/NJ. UPSTREAM STORMS CURRENTLY ACROSS NORTHERN WV/FAR
   SOUTHWEST PA AT 17Z SHOULD FURTHER INCREASE AND POTENTIALLY GROW
   UPSCALE OVER TIME...WHILE ADDITIONAL/SEMI-DISCRETE STORMS SHOULD
   ALSO DEVELOP/INCREASE JUST AHEAD OF/PERIPHERAL TO THIS ACTIVITY.
   INITIAL SIGNS OF THIS MAY ALREADY BE OCCURRING ACROSS CENTRAL PA
   COINCIDENT WITH A DEEPENING CU FIELD PER VISIBLE SATELLITE IMAGERY
   AMID AN INCREASINGLY UNSTABLE/WEAKLY INHIBITED WARM SECTOR. 

   ORGANIZED STORM MODES INCLUDING WHAT MAY BE A COMBINATION OF
   SEMI-DISCRETE SUPERCELLS AND AN UPSCALE-GROWING CONVECTIVE LINE/BOWS
   WILL BE AIDED BY A SEASONALLY STRONG STRENGTHENING BELT OF
   LOW/MID-TROPOSPHERIC WEST-SOUTHWESTERLY WINDS AS NOTED IN UPSTREAM
   UPPER-AIR OBSERVATIONS. DAMAGING WINDS CAN BE EXPECTED WITH THE
   STRONGER STORMS...WITH SOME TORNADO POTENTIAL AS WELL...PARTICULARLY
   IN CLOSER PROXIMITY TO THE SURFACE LOW/WARM FRONT ACROSS PA /AND
   EVENTUALLY NJ/.

   ..GUYER/MEAD.. 07/09/2015


   ATTN...WFO...PHI...BGM...CTP...LWX...PBZ...

   LAT...LON   41567536 40547523 38807635 39357922 40388015 41797697
               41567536 

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Page last modified: July 09, 2015
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