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WWUS20 KWNS 181614

SEL3

SPC WW 181614

DEZ000-MDZ000-NJZ000-NYZ000-PAZ000-CWZ000-182300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 643

NWS STORM PREDICTION CENTER NORMAN OK

1210 PM EDT TUE SEP 18 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       DELAWARE

       EASTERN MARYLAND

       NEW JERSEY

       FAR SOUTHEAST NEW YORK

       EASTERN PENNSYLVANIA

       COASTAL WATERS



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 1210 PM UNTIL

700 PM EDT.



TORNADOES...HAIL TO 0.5 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 95 STATUTE

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

NEW YORK TO 30 MILES WEST SOUTHWEST OF PHILADELPHIA PENNSYLVANIA.

 FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU3).



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...CONTINUE...WW 641...WW 642...



DISCUSSION...FORCED BAND OF CONVECTION OVER CNTRL PA IS EXPECTED TO

INTENSIFY THIS AFTERNOON WITH ADDITIONAL MORE DISCRETE STORM

DEVELOPMENT POSSIBLE FARTHER E NEARER TO THE ATLANTIC COAST.

WIDESPREAD CLOUDS AND PRECIPITATION WILL LIMIT THE DEGREE OF AIR

MASS DESTABILIZATION.  HOWEVER...GIVEN THE VERY MOIST

ENVIRONMENT...SUFFICIENT INSTABILITY WILL DEVELOP TO SUPPORT TSTMS.

AS BOTH VERTICAL SHEAR AND FORCING FOR ASCENT CONTINUE TO INCREASE

THROUGH THE AFTERNOON...EXPECT A CORRESPONDING ORGANIZATION OF

STORMS INTO LEWP/BOW STRUCTURES AND POSSIBLY SUPERCELLS CAPABLE OF

TORNADOES AND DAMAGING WINDS.



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

SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE

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

400. MEAN STORM MOTION VECTOR 23040.





...MEAD

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