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337 

WWUS20 KWNS 211633

SEL7

SPC WW 211633

MEZ000-212200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 667

NWS STORM PREDICTION CENTER NORMAN OK

1235 PM EDT THU JUL 21 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND NORTHERN MAINE



EFFECTIVE THIS THURSDAY AFTERNOON AND EVENING FROM 1235 PM UNTIL

600 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 85

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

HOULTON MAINE TO 25 MILES WEST OF BANGOR MAINE.  FOR A COMPLETE

DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE

(WOUS64 KWNS WOU7).



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.



DISCUSSION...MCS OVER SE QUEBEC WILL PROGRESS EWD/ESEWD INTO MAINE

THIS AFTERNOON.  THOUGH CLOUDS HAVE IMPEDED SURFACE HEATING SOME

ACROSS MAINE...IT APPEARS THAT INSTABILITY AND FORCING FOR ASCENT

WITH A SHORTWAVE TROUGH OVER QUEBEC WILL BE SUFFICIENT TO MAINTAIN

THE MCS THROUGH THE AFTERNOON.  WEAK-MODERATE INSTABILITY AND

RELATIVELY STRONG VERTICAL SHEAR WILL SUPPORT BOTH EMBEDDED

SUPERCELLS AND BOW ECHOES CAPABLE OF PRODUCING DAMAGING WINDS AND

MARGINALLY SEVERE HAIL.  AN ISOLATED TORNADO CANNOT BE RULED OUT

THIS AFTERNOON WITH EMBEDDED SUPERCELL STRUCTURES...GIVEN THE

EXPECTED INCREASE IN LOW-LEVEL SHEAR...BUT THIS THREAT WILL BE

SECONDARY TO THE DAMAGING WIND THREAT.



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 28040.





...THOMPSON

