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146 

WWUS20 KWNS 271727

SEL7

SPC WW 271727

DCZ000-DEZ000-MDZ000-NJZ000-NYZ000-PAZ000-VAZ000-WVZ000-CWZ000-28010

0-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 227

NWS STORM PREDICTION CENTER NORMAN OK

125 PM EDT THU MAY 27 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       NORTHERN DELAWARE

       CENTRAL AND EASTERN MARYLAND

       MOST OF NEW JERSEY

       SOUTH CENTRAL AND SOUTHEAST NEW YORK

       CENTRAL AND EASTERN PENNSYLVANIA

       NORTHERN VIRGINIA

       THE EASTERN PANHANDLE OF WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 125 PM UNTIL

900 PM EDT.



HAIL TO 2 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 65

STATUTE MILES EAST AND WEST OF A LINE FROM 65 MILES NORTHEAST OF

BINGHAMTON NEW YORK TO 40 MILES WEST OF PATUXENT RIVER MARYLAND.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU7).



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...THUNDERSTORM DEVELOPMENT IS EXPECTED IN THE NEXT 1-2

HOURS ALONG A SLOW-MOVING SURFACE FRONT FROM ERN NY SWD TO NEAR THE

NJ/PA BORDER.  THE BOUNDARY LAYER CONTINUES TO WARM TO THE W OF THE

FRONT...WITH MODERATE INSTABILITY NOW PRESENT WITH WEAKENING

CONVECTIVE INHIBITION.  ADDITIONALLY...A WEAK MIDLEVEL VORTICITY

CENTER IS MOVING SSEWD FROM ONTARIO TOWARD CENTRAL NY...AND THIS

FEATURE MAY ALSO AID IN CONDITIONING THE ENVIRONMENT TO SUPPORT

THUNDERSTORM DEVELOPMENT.  STEEP LAPSE RATE PROFILES AND

MODERATE-STRONG INSTABILITY THIS AFTERNOON...AS WELL AS 25-40 KT

NNWLY MIDLEVEL FLOW...WILL FAVOR SWD MOVING MULTICELL CLUSTERS

CAPABLE OF PRODUCING DAMAGING WINDS AND LARGE HAIL.  SOME EMBEDDED

SUPERCELL STRUCTURES MAY OCCUR ALONG THE FRONT WHERE VERTICAL SHEAR

WILL BE SOMEWHAT STRONGER...AND THIS MAY LOCALLY ENHANCE THE

POTENTIAL FOR LARGE HAIL.



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

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 36025.





...THOMPSON

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