

973 

WWUS20 KWNS 281137

SEL1

SPC WW 281137

DCZ000-MDZ000-NCZ000-VAZ000-CWZ000-281900-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 251

NWS STORM PREDICTION CENTER NORMAN OK

740 AM EDT THU APR 28 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       MUCH OF MARYLAND

       A SMALL PART OF NORTHWEST AND NORTHEAST NORTH CAROLINA

       MUCH OF CENTRAL AND EASTERN VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS THURSDAY MORNING AND AFTERNOON FROM 740 AM UNTIL

300 PM EDT.



TORNADOES...HAIL TO 1.5 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 80 STATUTE

MILES EAST AND WEST OF A LINE FROM 35 MILES NORTH NORTHEAST OF

BALTIMORE MARYLAND TO 35 MILES EAST OF DANVILLE VIRGINIA.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU1).



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 247. WATCH NUMBER 247 WILL NOT BE IN EFFECT AFTER

740 AM EDT. CONTINUE...WW 249...WW 250...



DISCUSSION...A BROKEN BAND OF CONVECTION CONTINUES TO DEVELOP E OF

THE BLUE RIDGE AND THE SYNOPTIC COLD FRONT.  A BREAK IN THE

CONVECTION IN NC IS ALLOWING AN UNIMPEDED INFLUX OF LOW-LEVEL

MOISTURE INTO VA...AND VERTICAL SHEAR PROFILES REMAIN STRONG.  GIVEN

THE STRONG SHEAR AND MOIST PROFILES WITH WEAK INSTABILITY...THE

POTENTIAL FOR A FEW TORNADOES AND DAMAGING WINDS WITH

SUPERCELLS/BOWS WILL CONTINUE THROUGH AT LEAST MIDDAY OR EARLY

AFTERNOON.



AVIATION...TORNADOES AND 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 22045.





...THOMPSON

