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048 

WWUS20 KWNS 051938

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SPC WW 051938

DCZ000-DEZ000-MDZ000-NJZ000-PAZ000-VAZ000-CWZ000-060100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 564

NWS STORM PREDICTION CENTER NORMAN OK

340 PM EDT SUN AUG 5 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       NORTHERN DELAWARE

       CENTRAL MARYLAND

       WESTERN NEW JERSEY

       SOUTHEAST PENNSYLVANIA

       NORTHERN VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 340 PM UNTIL 900

PM EDT.



HAIL TO 1 INCH 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 40 MILES SOUTH

SOUTHWEST OF WASHINGTON DISTRICT OF COLUM TO 20 MILES NORTH OF

ALLENTOWN PENNSYLVANIA.  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.



OTHER WATCH INFORMATION...CONTINUE...WW 563...



DISCUSSION...CONVECTION FORMING OVER E EDGE OF THE HIGHER TERRAIN

FROM NRN VA INTO SE PA SHOULD CONTINUE TO SPREAD EWD THROUGH THE

AFTERNOON/EVENING.  MODERATE INSTABILITY IS PRESENT AHEAD OF THESE

STORMS...WHERE SURFACE TEMPERATURES HAVE WARMED INTO THE LOW 90S

WITH DEWPOINTS IN THE LOW 70S.  GIVEN THE COMBINATION OF MLCAPE OF

1500-2500 J/KG PER THE 18Z IAD SOUNDING...AND ROUGHLY 30 KT

LOW-MIDLEVEL SWLY FLOW...THE STRONGER STORMS COULD PRODUCE A FEW

DAMAGING OUTFLOW GUSTS THROUGH THIS EVENING.



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

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60 KNOTS.

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

VECTOR 26020.





...THOMPSON

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