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WWUS20 KWNS 272237

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URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 654

NWS STORM PREDICTION CENTER NORMAN OK

635 PM EDT THU SEP 27 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       PARTS OF MARYLAND

       NORTHERN VIRGINIA

       EASTERN WEST VIRGINIA PANHANDLE

       COASTAL WATERS



EFFECTIVE THIS THURSDAY NIGHT FROM 635 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 35

STATUTE MILES EITHER SIDE OF A LINE FROM 25 MILES SOUTH SOUTHEAST

OF BALTIMORE MARYLAND TO 65 MILES WEST SOUTHWEST 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...A SMALL CUSTER OF PERSISTENT AND ORGANIZED STORMS

CONTINUES TO MOVE EAST ACROSS NRN VA THIS EVENING ASSOCIATED WITH AN

APPROACHING LOW-AMPLITUDE SHORT WAVE TROUGH CROSSING THE

APPALACHIANS. LIFT WITH THE SHORT WAVE WAS ARRIVING COINCIDENT WITH

DIURNAL MAXIMUM IN INSTABILITY ACROSS THE REGION AND THIS WILL

LIKELY SUSTAIN THE PROSPECTS FOR STRONG TO SEVERE STORMS EAST ACROSS

THE AREA INTO THE EVENING HOURS. A VEERED DEEP-LAYER WIND PROFILE

EVIDENT ON LWX VWP WAS RESULTING IN ADEQUATE SR FLOW AND SHEAR FOR

UPDRAFTS TO ACQUIRE OCCASIONAL MODEST ROTATION AND LARGE HAIL HAS

BEEN REPORTED FROM A COUPLE OF THE CELLS MOVING ACROSS THE WV/VA

BORDER.



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 450. MEAN STORM

MOTION VECTOR 26025.





...CARBIN

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