

000 

WWUS20 KWNS 271815

SEL1

SPC WW 271815

MDZ000-PAZ000-VAZ000-WVZ000-280200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 691

NWS STORM PREDICTION CENTER NORMAN OK

215 PM EDT THU SEP 27 2007



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       NORTHWEST MARYLAND

       MUCH OF PENNSYLVANIA

       NORTHERN VIRGINIA

       EASTERN WEST VIRGINIA



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 215 PM UNTIL

1000 PM EDT.



HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 85

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

NORTHEAST OF WILLIAMSPORT PENNSYLVANIA TO 65 MILES EAST SOUTHEAST

OF CHARLESTON WEST VIRGINIA.  FOR A COMPLETE DEPICTION OF THE

WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU1).



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 690...



DISCUSSION...STORMS ARE EXPECTED TO INCREASE AHEAD OF SMALL-SCALE

SHORT WAVE TROUGH EJECTING NORTHEASTWARD AHEAD OF A LARGER SCALE

TROUGH AMPLIFYING ACROSS THE UPPER MIDWEST/GREAT LAKES REGIONS.

AIRMASS WILL BE SUFFICIENTLY UNSTABLE TO SUPPORT VIGOROUS STORM

UPDRAFTS WITHIN INCREASINGLY SHEARED FLOW. FAST MOVING LINE SEGMENTS

AND A FEW SUPERCELLS ARE EXPECTED TO BECOME MORE LIKELY. THIS

ACTIVITY WILL BE ACCOMPANIED BY HAIL AND STRONG TO DAMAGING WINDS

OVER THE NEXT SEVERAL HOURS.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70 KNOTS.

A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 450. MEAN STORM MOTION

VECTOR 24035.





...CARBIN

