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Mesoscale Discussion 658
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   MESOSCALE DISCUSSION 0658
   NWS STORM PREDICTION CENTER NORMAN OK
   0521 AM CDT THU APR 28 2011
   
   AREAS AFFECTED...ERN NY...ERN PA...WRN NJ...DE...EXTREME ERN MD
   
   CONCERNING...SEVERE THUNDERSTORM WATCH 249...
   
   VALID 281021Z - 281115Z
   
   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 249
   CONTINUES.
   
   A NEARLY SOLID QLCS WILL CONTINUE MOVING NEWD AT 40 TO 50 KT ACROSS
   PORTIONS OF ERN NY AND NERN PA...AND MOVE INTO THE HUDSON VALLEY AND
   ALBANY AREA DURING THE NEXT HALF HOUR TO HOUR. MARGINAL INSTABILITY
   PRECEDING THE QLCS WILL ALLOW IT TO BE MAINTAINED AS IT CONTINUES
   TRACKING NORTHEAST...GIVEN EFFECTIVE BULK SHEAR MAGNITUDES AROUND 60
   KT. AS SUCH...THE WW MAY NEED TO BE EXTENDED EWD TO THE NEW YORK
   BORDER. THE PRIMARY THREAT WILL CONTINUE TO BE DMGG WINDS...GIVEN
   SSWLY WINDS OF 40-50 KT AROUND 1 KM AGL PER ALBANY VWP.
   HOWEVER...WITH 0-1-KM STORM-RELATIVE HELICITY VALUES DERIVED FROM
   THE VWP OF 313 M2/S2 SUGGESTING STRONG LOW-LEVEL VERTICAL WIND
   SHEAR...THE THREAT FOR ONE OR TWO TORNADOES ASSOCIATED WITH EMBEDDED
   MESOVORTEX WILL BE PRESENT. AS THE ACTIVITY SHIFTS FARTHER EAST INTO
   NEW ENGLAND...IT WILL ENCOUNTER GROWING CINH AMIDST THE MORE STABLE
   MARINE LAYER...TEMPERING THE OVERALL SVR THREAT. MEANWHILE...
   SCATTERED CONVECTION FARTHER SOUTH OF THE QLCS ACROSS WW249 WILL
   CONTINUE MOVING NEWD...AS WELL...POSING A THREAT FOR DMGG WINDS.
   HOWEVER...THE LACK OF MORE ORGANIZED CONVECTIVE STRUCTURES COULD
   MITIGATE THE POTENTIAL TO SOME DEGREE.
   
   ..COHEN.. 04/28/2011
   
   
   ATTN...WFO...OKX...ALY...PHI...BGM...CTP...
   
   LAT...LON   38817499 38857580 39237590 39687571 40197642 41227595
               42867554 43697415 43467336 43017341 41147374 40837427
               38817499 
   
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Page last modified: April 28, 2011
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