

000 

WWUS20 KWNS 021758

SEL3

SPC WW 021758

DCZ000-MDZ000-PAZ000-VAZ000-WVZ000-CWZ000-030000-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 793

NWS STORM PREDICTION CENTER NORMAN OK

155 PM EDT SAT AUG 2 2008



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       MARYLAND

       SOUTHERN PENNSYLVANIA

       NORTHERN VIRGINIA

       NORTHERN AND EASTERN WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 155 PM UNTIL

800 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 120

STATUTE MILES EAST AND WEST OF A LINE FROM 35 MILES WEST

NORTHWEST OF HAGERSTOWN MARYLAND TO 20 MILES WEST SOUTHWEST OF

STAUNTON VIRGINIA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).



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 791...WW 792...



DISCUSSION...AT LEAST TWO BANDS OF ISOLATED STORMS ARE NOW

DEVELOPING ACROSS PARTS OF THE UPPER OH VALLEY AND CNTRL

APPALACHIANS ASSOCIATED WITH DEEPENING TROUGH/FRONTAL PASSAGE OVER

THE REGION. POCKETS OF STRONG HEATING HAVE BOOSTED INSTABILITY WITH

MLCAPE VALUES AOA 1000 J/KG AMIDST STRENGTHENING DEEP-LAYER SHEAR

SUPPORTIVE OF ORGANIZED/PERSISTENT UPDRAFTS. EXPECT ACTIVITY TO

CONTINUE TO EXPAND IN AREAL COVERAGE THROUGH THE AFTERNOON WITH

SUPERCELLS AND/OR RELATIVELY FAST-MOVING LINE SEGMENTS PRODUCING

DAMAGING WINDS AND HAIL.



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 29030.





...CARBIN

