WATCHES: Urgent - Immediate Broadcast Requested

WWUS20 KWNS 181659
SEL5
SPC WW 181659
DCZ000-DEZ000-MDZ000-NJZ000-OHZ000-PAZ000-VAZ000-WVZ000-CWZ000-19010
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URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 305
NWS STORM PREDICTION CENTER NORMAN OK
1255 PM EDT WED MAY 18 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

DISTRICT OF COLUMBIA
DELAWARE
MARYLAND
SOUTHERN NEW JERSEY
SOUTHEAST OHIO
SOUTHERN AND WESTERN PENNSYLVANIA
NORTHERN AND CENTRAL VIRGINIA
EASTERN WEST VIRGINIA
COASTAL WATERS

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 1255 PM UNTIL
900 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 75
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 5 MILES WEST OF
WHEELING WEST VIRGINIA TO 10 MILES NORTH NORTHEAST OF WALLOPS
VIRGINIA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU5).

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...TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND
INTENSITY THIS AFTERNOON IN ADVANCE OF VORTICITY MAXIMUM PIVOTING
NWWD ACROSS THE REGION. OBSERVATION AND RUC DIAGNOSTIC DATA
INDICATE THAT THE AIR MASS HAS BECOME MODERATELY UNSTABLE WITH
SBCAPE VALUES OF 1000-1500 J/KG. WHEN COUPLED WITH PRESENCE OF
40-50 KT MIDLEVEL JET STREAK ATTENDANT TO VORTICITY MAXIMUM...SETUP
WILL FAVOR THE DEVELOPMENT OF ORGANIZED STORMS INCLUDING SUPERCELLS
AND LINE SEGMENTS CAPABLE OF SEVERE HAIL AND DAMAGING WIND GUSTS.
AMBIENT LOW-LEVEL SHEAR WILL REMAIN RATHER WEAK TODAY...HOWEVER A
TORNADO WILL BE POSSIBLE WITH STORMS THAT CAN FAVORABLY INTERACT
WITH ANY DIFFERENTIAL HEATING/OUTFLOW BOUNDARIES THAT CAN BECOME
MORE DISTINCT THIS AFTERNOON.

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 400. MEAN STORM
MOTION VECTOR 15530.

...MEAD

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