

000 

WWUS20 KWNS 252159

SEL2

SPC WW 252159

DCZ000-MDZ000-OHZ000-PAZ000-VAZ000-WVZ000-CWZ000-260300-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 652

NWS STORM PREDICTION CENTER NORMAN OK

555 PM EDT SAT AUG 25 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       CENTRAL AND WESTERN MARYLAND

       SOUTHEAST OHIO

       MUCH OF PENNSYLVANIA

       NORTHERN VIRGINIA

       CENTRAL AND NORTHERN WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 555 PM UNTIL

1100 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 140

STATUTE MILES EAST AND WEST OF A LINE FROM 45 MILES NORTH

NORTHWEST OF WILLIAMSPORT PENNSYLVANIA TO 45 MILES SOUTH

SOUTHWEST OF ELKINS WEST VIRGINIA.  FOR A COMPLETE DEPICTION OF

THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS

WOU2).



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 650...WW 651...



DISCUSSION...THUNDERSTORMS WILL CONTINUE TO DEVELOP ALONG THE COLD

FRONT MOVING EWD/SEWD ACROSS OH INTO WV/PA THIS EVENING.  MODERATE

INSTABILITY AND VERTICAL SHEAR IN THE WARM SECTOR WILL SUPPORT

ORGANIZED LINE SEGMENTS AND MULTICELL CLUSTERS...WITH THE THREAT FOR

DAMAGING WINDS AND LARGE HAIL.  FARTHER E...SEVERAL CLUSTERS OF

STORMS FROM NRN VA INTO ERN PA WILL DRIFT E OF THE HIGHER TERRAIN

AND BE MAINTAINED BY A VERY WARM/MOIST ENVIRONMENT WITH STRONG

INSTABILITY NEAR AND W OF THE I-95 CORRIDOR.  THOUGH VERTICAL SHEAR

IS WEAK THIS FAR E...THE STRONG INSTABILITY SHOULD SUPPORT A

CONTINUED THREAT FOR DAMAGING WET MICROBURSTS AND ISOLATED HAIL INTO

THE LATE EVENING.



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 27030.





...THOMPSON

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