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Mesoscale Discussion 1689
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   MESOSCALE DISCUSSION 1689
   NWS STORM PREDICTION CENTER NORMAN OK
   0558 PM CDT SAT SEP 06 2014

   AREAS AFFECTED...NRN VA...MD...DE...NJ...SE PA

   CONCERNING...SEVERE THUNDERSTORM WATCH 498...

   VALID 062258Z - 070030Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 498
   CONTINUES.

   SUMMARY...A SEVERE THREAT SHOULD CONTINUE FOR A COUPLE MORE HOURS
   ACROSS PARTS SE PA...NJ...DE AND MD BEFORE DIMINISHING. WIND DAMAGE
   AND HAIL WILL BE PRIMARY THREATS.

   DISCUSSION...LATEST SFC ANALYSIS SHOWS A COLD FRONT LOCATED FROM
   CNTRL PA SWWD INTO WV WITH A PRE-FRONTAL TROUGH LOCATED ALONG THE
   COAST FROM NY INTO ERN MD. SFC DEWPOINTS ALONG THE SFC TROUGH ARE IN
   THE UPPER 60S AND LOWER 70S F WHICH HAS RESULTED IN MODERATE
   INSTABILITY ACROSS MUCH OF THE REGION. RAP DATA SUGGESTS THAT MLCAPE
   IS IN THE 1500 TO 2000 J/KG ACROSS THE SRN TWO-THIRDS OF WW 498
   WHERE LOW-LEVEL LAPSE RATES WERE ALSO STEEP. THIS ALONG WITH ABOUT
   30 KT OF DEEP-LAYER SHEAR EVIDENT ON THE DOVER DELAWARE WSR-88D VWP
   SHOULD BE SUFFICIENT FOR AN ISOLATED WIND DAMAGE THREAT. FURTHER TO
   THE NORTH ACROSS SERN PA INTO NJ...DEEP-LAYER SHEAR WAS STRONGER DUE
   TO THE INFLUENCE FROM THE ENTRANCE REGION OF MID-LEVEL JET PASSING
   TO THE NORTH. THIS ALONG WITH A BIT STRONGER LOW-LEVEL SHEAR MAY BE
   ENOUGH FOR A FEW ROTATING STORMS. THESE STORMS MAY HAVE THE
   POTENTIAL FOR HAIL AND DAMAGING WIND GUSTS.

   ..BROYLES/MEAD.. 09/06/2014


   ATTN...WFO...OKX...PHI...BGM...AKQ...CTP...LWX...

   LAT...LON   38347472 38467510 38417563 38657572 38677594 38647615
               38647623 38497633 38307632 38337658 38517672 38347684
               38157686 38397702 38337718 38377731 38517730 38557753
               38857768 38927767 38987794 39127788 39367824 39567818
               39587798 39667808 39617824 39697834 39747811 40327762
               40557708 40817632 40947622 40937595 41017582 41087572
               41197553 41227514 41117510 41077491 41337475 41357463
               41227436 41047452 40987430 40897428 40637444 40627423
               40557419 40447423 40447392 40267362 39617380 39077422
               39007435 38787455 38627473 38347472 

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Page last modified: September 07, 2014
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