

314 

WWUS20 KWNS 091918

SEL4

SPC WW 091918

DEZ000-MDZ000-NJZ000-PAZ000-CWZ000-100200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 684

NWS STORM PREDICTION CENTER NORMAN OK

315 PM EDT SUN AUG 9 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHERN DELAWARE

       EXTREME NORTHEAST MARYLAND

       NEW JERSEY

       CENTRAL AND EASTERN PENNSYLVANIA

       COASTAL WATERS



EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 315 PM UNTIL

1000 PM EDT.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

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



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 75

STATUTE MILES EITHER SIDE OF A LINE FROM 25 MILES WEST OF ALTOONA

PENNSYLVANIA TO 50 MILES NORTH NORTHEAST OF TRENTON NEW JERSEY.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 682...WW 683...



DISCUSSION...SQUALL LINE WITH EMBEDDED LEWPS/BOW ECHOES IS EXPECTED

TO MOVE SEWD OVER THE NEXT SEVERAL HOURS.  AIR MASS HAS BEEN

DESTABILIZING AS THE WARM FRONT MOVES SLOWLY NEWD...WITH MLCAPE OF

1000-1500 J/KG ALONG WEST OF THE FRONT.  WNWLY 30-35 KT MID LEVEL

FLOW IS RESULTING IN FAVORABLE VERTICAL SHEAR TO MAINTAIN MESOSCALE

CONVECTIVE ORGANIZATION.  STRONGER STORMS WILL BE CAPABLE OF

PRODUCING DAMAGING WIND GUSTS AND OCCASIONAL HAIL.



AVIATION...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 28025.





...WEISS

