

000 

WWUS20 KWNS 271528

SEL9

SPC WW 271528

DCZ000-DEZ000-MDZ000-NJZ000-PAZ000-VAZ000-CWZ000-280000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 759

NWS STORM PREDICTION CENTER NORMAN OK

1125 AM EDT SUN JUL 27 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       DELAWARE

       MUCH OF MARYLAND

       NEW JERSEY

       SOUTHEAST PENNSYLVANIA

       NORTHERN VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS SUNDAY MORNING AND EVENING FROM 1125 AM UNTIL 800

PM EDT.



HAIL TO 2 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH OF

TRENTON NEW JERSEY TO 45 MILES WEST SOUTHWEST OF PATUXENT RIVER

MARYLAND.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



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...SCATTERED THUNDERSTORMS WILL INTENSIFY DURING THE

AFTERNOON ALONG A SURFACE COLD FRONT AND DIFFUSE LEE TROUGH...IN

ADVANCE OF A MID LEVEL SHORTWAVE TROUGH.  RELATIVELY STEEP LOW-MID

LEVEL LAPSE RATES AND STRONG SURFACE HEATING WILL RESULT IN MLCAPE

VALUES AOA 2000 J/KG THIS AFTERNOON...WHILE EFFECTIVE BULK SHEAR

AROUND 30 KT WILL SUPPORT ORGANIZED MULTICELL CLUSTERS/LINES...AND

PERHAPS SOME MARGINAL SUPERCELL STRUCTURES.  DAMAGING WINDS AND

LARGE HAIL WILL BE THE MAIN SEVERE THREATS THROUGH THE

AFTERNOON/EVENING.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

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

MOTION VECTOR 27025.





...THOMPSON

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