

000 

WWUS20 KWNS 212106

SEL7

SPC WW 212106

DCZ000-MDZ000-VAZ000-WVZ000-CWZ000-220200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 437

NWS STORM PREDICTION CENTER NORMAN OK

510 PM EDT THU JUN 21 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       MARYLAND

       FAR NORTHERN VIRGINIA

       FAR NORTHEASTERN WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 510 PM UNTIL

1000 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 35

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 50 MILES WEST

NORTHWEST OF MARTINSBURG WEST VIRGINIA TO 35 MILES SOUTHEAST OF

BALTIMORE MARYLAND.  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.



OTHER WATCH INFORMATION...CONTINUE...WW 434...WW 435...WW 436...



DISCUSSION...SMALL LINE/LINES OF STORMS WILL BRING A RISK OF

DAMAGING WINDS AS THEY PROGRESS ESEWD INTO THE CHESAPEAKE REGION

THROUGH THE EVENING.  STEEP LOW LEVEL LAPSE RATES AND STRONG NWLY

FLOW ALOFT MAY SUSTAIN STRONG TO SEVERE WINDS PRIOR TO

SUNSET...DESPITE THE MEAGER INSTABILITY.



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 400. MEAN STORM MOTION

VECTOR 32035.





...EVANS

