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WWUS20 KWNS 272213

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URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 240

NWS STORM PREDICTION CENTER NORMAN OK

615 PM EDT WED APR 27 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       MARYLAND

       NORTHERN NORTH CAROLINA

       CENTRAL AND EASTERN VIRGINIA

       EASTERN WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 615 PM

UNTIL 200 AM EDT.



TORNADOES...HAIL TO 2 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE

MILES EAST AND WEST OF A LINE FROM 15 MILES NORTHEAST OF

MARTINSBURG WEST VIRGINIA TO 30 MILES WEST SOUTHWEST OF RALEIGH

NORTH CAROLINA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU0).



REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR

TORNADOES AND 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.



OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO

WATCH NUMBER 233. WATCH NUMBER 233 WILL NOT BE IN EFFECT AFTER

615 PM EDT. CONTINUE...WW 232...WW 234...WW 235...WW 236...WW

237...WW 238...WW 239...



DISCUSSION...TSTMS HAVE RAPIDLY INTENSIFIED THIS EVENING WITHIN A

MOIST AND MODERATELY UNSTABLE ENVIRONMENT WITH MLCAPE VALUES OF

1000-2000 J/KG.  DEEP-LAYER VERTICAL SHEAR IS ALREADY SUPPORTIVE OF

SUPERCELLS...AND LOW-LEVEL SHEAR IS FORECAST TO STRENGTHEN THROUGH

THE REMAINDER OF THE EVENING WITH EFFECTIVE SRH VALUES APPROACHING

250-300 M2/S2.  AS SUCH...THE POTENTIAL FOR TORNADOES WILL EXIST IN

ADDITION TO DAMAGING WINDS AND HAIL.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

500. MEAN STORM MOTION VECTOR 24035.





...MEAD

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