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000 

WWUS20 KWNS 200401

SEL7

SPC WW 200401

DCZ000-MDZ000-VAZ000-CWZ000-200800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 137

NWS STORM PREDICTION CENTER NORMAN OK

1200 AM EDT THU MAR 20 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       CENTRAL MARYLAND

       NORTHEAST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS THURSDAY MORNING FROM MIDNIGHT UNTIL 400 AM EDT.



HAIL TO 0.5 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 40

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH

NORTHEAST OF BALTIMORE MARYLAND TO 55 MILES SOUTH SOUTHWEST OF

WASHINGTON DISTRICT OF COLUM.  FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).



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...LOW-TOPPED CONVECTIVE BAND ACROSS CENTRAL/N CENTRAL VA

HAS INTENSIFIED SOME IN THE PAST HOUR.  THOUGH INSTABILITY REMAINS

QUITE MARGINAL...55-70 KT FLOW COULD BE TRANSPORTED TO THE SURFACE

IN THE HEAVIER PRECIPITATION CORES.



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

TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 350. MEAN STORM

MOTION VECTOR 25045.





...THOMPSON

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