

162 

WWUS20 KWNS 181659

SEL5

SPC WW 181659

DCZ000-DEZ000-MDZ000-NJZ000-OHZ000-PAZ000-VAZ000-WVZ000-CWZ000-19010

0-



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

