Nelson County, Virginia

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.