

000 

WWUS20 KWNS 302054

SEL4

SPC WW 302054

DCZ000-DEZ000-MDZ000-NJZ000-PAZ000-VAZ000-CWZ000-310400-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 774

NWS STORM PREDICTION CENTER NORMAN OK

455 PM EDT WED JUL 30 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       DELAWARE

       MUCH OF MARYLAND

       SOUTHWEST NEW JERSEY

       SOUTHEAST PENNSYLVANIA

       NORTHEAST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS WEDNESDAY AFTERNOON FROM 455 PM UNTIL MIDNIGHT EDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 50

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES WEST

NORTHWEST OF TRENTON NEW JERSEY TO 40 MILES SOUTH SOUTHEAST OF

WASHINGTON DISTRICT OF COLUM.  FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



DISCUSSION...THUNDERSTORMS ARE FORMING ALONG A LEE TROUGH FROM SE PA

INTO NRN VA.  THIS ACTIVITY MAY INTENSIFY THIS EVENING AS AN

UPSTREAM SHORTWAVE TROUGH PROGRESSES ESEWD FROM PA.  THE COMBINATION

OF MODERATE INSTABILITY AND EFFECTIVE BULK SHEAR AROUND 40 KT WILL

SUPPORT A THREAT FOR SUPERCELLS AND ORGANIZED MULTICELL CLUSTERS.

DAMAGING WINDS AND LARGE HAIL WILL BE THE MAIN THREATS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 28025.





...THOMPSON

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