WATCHES: Severe Thunderstorm Watch Number 426

WWUS20 KWNS 281714
SEL6
SPC WW 281714
DCZ000-DEZ000-MDZ000-NJZ000-PAZ000-VAZ000-CWZ000-290000-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 426
NWS STORM PREDICTION CENTER NORMAN OK
110 PM EDT MON JUN 28 2010

THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF

DISTRICT OF COLUMBIA
DELAWARE
MUCH OF MARYLAND
NEW JERSEY
SOUTHEAST PENNSYLVANIA
NORTHERN VIRGINIA
COASTAL WATERS

EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 110 PM UNTIL 800
PM EDT.

HAIL TO 1 INCH 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 60
STATUTE MILES EITHER SIDE OF A LINE FROM 55 MILES SOUTHWEST OF
WASHINGTON DISTRICT OF COLUM TO 30 MILES NORTHEAST OF TRENTON NEW
JERSEY. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED
WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6).

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.

DISCUSSION...SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP IN THE
NEXT COUPLE OF HOURS IMMEDIATELY E OF THE HIGH TERRAIN...ALONG A
DIFFERENTIAL HEATING BOUNDARY FROM NRN VA INTO SE PA. SURFACE
TEMPERATURES IN THE 90S TO THE E OF THE CLOUD BOUNDARY AND BOUNDARY
LAYER DEWPOINTS OF 68-72 F ARE CONTRIBUTING TO MODERATE
INSTABILITY...ALONG THE SRN FRINGE OF THE STRONGER MIDLEVEL
FLOW/SHEAR. THE MODERATE FLOW/INSTABILITY AND RELATIVELY DEEP
SURFACE MIXED LAYER WILL SUPPORT DAMAGING GUSTS WITH ORGANIZED
MULTICELL CLUSTERS...AND POTENTIALLY SOME EMBEDDED BOW/SUPERCELL
STRUCTURES THROUGH THE AFTERNOON/EVENING AS STORMS APPROACH THE
COAST.

AVIATION...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 27030.

...THOMPSON

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