

287 

WWUS20 KWNS 132029 CCA

SEL6

SPC WW 132029 CCA

DCZ000-MDZ000-VAZ000-CWZ000-140100-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 866...CORRECTED

NWS STORM PREDICTION CENTER NORMAN OK

435 PM EDT THU OCT 13 2011



CORRECTED FOR WATCH EXPIRATION TIME



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       SOUTHERN MARYLAND

       EASTERN VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 435 PM UNTIL

900 PM EDT.



TORNADOES...HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS

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



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 50 STATUTE

MILES EAST AND WEST OF A LINE FROM 20 MILES NORTH OF WASHINGTON

DISTRICT OF COLUM TO 35 MILES EAST SOUTHEAST OF RICHMOND

VIRGINIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).



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.



DISCUSSION...A SMALL CLUSTER OF SUPERCELLS HAS EVOLVED THIS

AFTERNOON INVOF OF A WARM/QUASI-STATIONARY BOUNDARY WHERE AIR MASS

IS MOIST AND MODERATELY UNSTABLE WITH MLCAPE OF AROUND 1000 J/KG.

THOUGH AMBIENT VERTICAL SHEAR IS NOT PARTICULARLY

STRONG...VERTICALLY VEERING WIND PROFILES COUPLED WITH THE MOIST/LOW

LCL BOUNDARY LAYER AND VORTICITY ENHANCEMENT ALONG THE SURFACE

BOUNDARY WILL ENHANCE LOW-LEVEL STORM ROTATION AND THE POTENTIAL FOR

A FEW TORNADOES.



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

SURFACE AND ALOFT TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND

GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500.

MEAN STORM MOTION VECTOR 20025.





...MEAD

