

014 

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

