

000 

WWUS20 KWNS 121556

SEL1

SPC WW 121556

MDZ000-VAZ000-CWZ000-122200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 201

NWS STORM PREDICTION CENTER NORMAN OK

1155 AM EDT SAT APR 12 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN MARYLAND

       SOUTHEAST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS SATURDAY MORNING AND EVENING FROM 1155 AM UNTIL

600 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 70

STATUTE MILES EAST AND WEST OF A LINE FROM 25 MILES NORTH OF

WALLOPS VIRGINIA TO 55 MILES WEST SOUTHWEST OF NORFOLK VIRGINIA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU1).



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...SLIGHTLY ELEVATED CONVECTION THIS MORNING IN ADVANCE OF

THE COLD FRONT WILL GRADUALLY BECOME SURFACE-BASED AS THE LOW LEVELS

DESTABILIZE VIA DAYTIME HEATING.  MLCAPE VALUES OF 500-1000 J/KG...

DEEP UNIDIRECTIONAL WIND PROFILES...AND 50 KT FLOW WITHIN A FEW

THOUSAND FT OF THE GROUND WILL SUPPORT A THREAT FOR BOWS/SUPERCELLS

WITH DAMAGING WINDS AND MARGINALLY SEVERE HAIL THROUGH THE

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 500. MEAN STORM

MOTION VECTOR 25055.





...THOMPSON

