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WWUS20 KWNS 161814

SEL0

SPC WW 161814

DCZ000-MDZ000-VAZ000-WVZ000-CWZ000-170200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 620

NWS STORM PREDICTION CENTER NORMAN OK

215 PM EDT MON AUG 16 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       DISTRICT OF COLUMBIA

       CENTRAL AND EASTERN MARYLAND

       NORTHERN VIRGINIA

       FAR EASTERN WEST VIRGINIA

       COASTAL WATERS



EFFECTIVE THIS MONDAY AFTERNOON AND EVENING FROM 215 PM UNTIL

1000 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 60

STATUTE MILES EAST AND WEST OF A LINE FROM 40 MILES NORTH

NORTHWEST OF BALTIMORE MARYLAND TO 50 MILES SOUTHEAST OF

CHARLOTTESVILLE 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 619...



DISCUSSION...TSTMS DEVELOPING ALONG THE BLUE RIDGE SHOULD CONTINUE

TO INTENSIFY WHILE PROGRESSING EWD/SEWD INTO A HOT AND MODERATELY

UNSTABLE AIR MASS WITH MLCAPE OF 2000-2500 J/KG.  17Z IAD SOUNDING

LIKELY REPRESENTS A GOOD PROXY FOR THERMODYNAMIC AND KINEMATIC

ENVIRONMENT ACROSS THE AREA...THOUGH MODEL GUIDANCE AND

OBSERVATIONAL DATA SUGGEST VERTICAL SHEAR DIMINISHES WITH SWD

EXTENT.  AS SUCH...GIVEN ENVIRONMENT WILL BE SUPPORTIVE OF ORGANIZED

MULTICELL AND PERHAPS SUPERCELL STORM MODES WITH THE PRIMARY HAZARD

BEING DAMAGING WIND GUSTS.



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 28025.





...MEAD

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