

672 

WWUS20 KWNS 120121

SEL1

SPC WW 120121

DCZ000-MDZ000-NYZ000-PAZ000-VAZ000-WVZ000-CWZ000-120600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 21

NWS STORM PREDICTION CENTER NORMAN OK

820 PM EST WED FEB 11 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       MARYLAND

       SOUTHWEST NEW YORK

       CENTRAL PENNSYLVANIA

       NORTHERN AND CENTRAL VIRGINIA

       FAR EASTERN PANHANDLE OF WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS WEDNESDAY NIGHT AND THURSDAY MORNING FROM 820 PM

UNTIL 100 AM EST.



HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

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 15 MILES EAST OF

RICHMOND VIRGINIA TO 60 MILES NORTHEAST OF JAMESTOWN NEW YORK.

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.



OTHER WATCH INFORMATION...CONTINUE...WW 18...WW 19...WW 20...



DISCUSSION...LEADING EDGE OF INTENSE VERTICAL MOTION ALONG FAST

MOVING COLD FRONT/SQUALL LINE CONTINUES TO PRODUCE SEVERE WINDS WITH

MEASURED GUSTS IN EXCESS OF 50 KT OVER MUCH OF THE CENTRAL

APPALACHIANS.  AS MAIN UPPER SYSTEM AND ASSOCIATED JET MAXIMA ROTATE

ENEWD...EXPECT THREAT OF DAMAGING WINDS WILL BE MAINTAINED ALONG

NARROW LINE OF MOIST CONVECTION WITH OR WITHOUT OCCASIONAL LIGHTNING

STRIKES.  WIND DAMAGE THREAT MAY BE WIDESPREAD WITH THE MORE INTENSE

LINE SEGMENTS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 350. MEAN STORM

MOTION VECTOR 26050.





...EVANS

