

984 

WWUS20 KWNS 121749

SEL7

SPC WW 121749

DCZ000-DEZ000-MDZ000-NCZ000-PAZ000-VAZ000-WVZ000-CWZ000-130000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 467

NWS STORM PREDICTION CENTER NORMAN OK

150 PM EDT SUN JUN 12 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       NORTHERN DELAWARE

       MARYLAND

       A SMALL PART OF NORTHWEST NORTH CAROLINA

       SOUTHEAST PENNSYLVANIA

       VIRGINIA

       THE EASTERN WEST VIRGINIA PANHANDLE

       COASTAL WATERS



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 150 PM UNTIL 800

PM 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 95

STATUTE MILES EAST AND WEST OF A LINE FROM 10 MILES EAST OF

HARRISBURG PENNSYLVANIA TO 55 MILES SOUTH OF LYNCHBURG VIRGINIA.

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...THUNDERSTORMS ARE STRENGTHENING ALONG THE COLD FRONT IN

PA...AND ADDITIONAL DEVELOPMENT IS BEGINNING FARTHER TO THE S/SW

OVER THE HIGHER TERRAIN AND IN THE OPEN WARM SECTOR.  STRONG SURFACE

HEATING IS SUPPORTING MLCAPE VALUES OF 1500-2000 J/KG...WHILE

VERTICAL SHEAR IS SUFFICIENT FOR ORGANIZED CLUSTERS FROM NRN VA INTO

PA.  FARTHER S...THE ENVIRONMENT IS MORE FAVORABLE FOR PULSE TYPE

SEVERE STORMS WITH DAMAGING DOWNBURSTS...GIVEN THE WEAKER VERTICAL

SHEAR AND STEEP LOW-LEVEL LAPSE RATES.  DAMAGING WINDS WILL BE THE

MAIN SEVERE THREAT...THOUGH MARGINALLY SEVERE HAIL WILL ALSO BE

POSSIBLE IN THE STRONGER STORMS.



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 500. MEAN STORM

MOTION VECTOR 30025.





...THOMPSON

