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607 

WWUS20 KWNS 042155

SEL0

SPC WW 042155

DCZ000-MDZ000-PAZ000-VAZ000-WVZ000-CWZ000-050500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 570

NWS STORM PREDICTION CENTER NORMAN OK

550 PM EDT WED AUG 4 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       WESTERN AND CENTRAL MARYLAND

       SOUTH CENTRAL PENNSYLVANIA

       WESTERN...CENTRAL AND NORTHERN VIRGINIA

       SOUTHEAST WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS WEDNESDAY AFTERNOON AND THURSDAY MORNING FROM 550

PM UNTIL 100 AM 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 65

STATUTE MILES EITHER SIDE OF A LINE FROM 25 MILES NORTHWEST OF

HARRISBURG PENNSYLVANIA TO 25 MILES SOUTH OF ROANOKE VIRGINIA.

FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH

OUTLINE UPDATE (WOUS64 KWNS WOU0).



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 567...WW 568...WW 569...



DISCUSSION...BASED ON AREA WIND AND SFC-BASED INSTABILITY

CONSIDERATIONS... CNTRL WV/SW PA MCS EXPECTED TO CONTINUE ESE TOWARD

KBWI...WHILE SRN PART OF MCS TURNS MORE SE TOWARD KROA.  MODERATE

MEAN WIND FIELD...PW...AND INSTABILITY LEVELS SUGGEST CONTINUED RISK

FOR BOWING SEGMENTS WITH DMGG WIND IN NRN SECTION.  FARTHER

SW...WEAKER WIND FIELD MAY BE COMPENSATED BY SOMEWHAT GREATER

INSTABILITY TO MAINTAIN A RISK FOR LOCALLY DMGG WIND WITH SRN PART

OF SYSTEM AS IT MOVES SEWD INTO SW VA.



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 29030.





...CORFIDI

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