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WWUS20 KWNS 040728

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NYZ000-LEZ000-LOZ000-041500-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 831

NWS STORM PREDICTION CENTER NORMAN OK

325 AM EDT SUN SEP 4 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN AND CENTRAL NEW YORK

       LAKE ERIE

       LAKE ONTARIO



EFFECTIVE THIS SUNDAY MORNING FROM 325 AM UNTIL 1100 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 45

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES WEST

NORTHWEST OF JAMESTOWN NEW YORK TO 45 MILES EAST OF WATERTOWN NEW

YORK.  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 830...



DISCUSSION...A SMALL CLUSTER OF FORWARD-PROPAGATING STORMS HAS

EVOLVED OVER LK ERIE...DOWNSTREAM FROM A BAND OF

DEEP...UNIDIRECTIONAL WSW FLOW IN THE 850-500 MB LAYER.  SIMILAR TO

THE PREVIOUS TWO NIGHTS...THE MEAN FLOW IN THIS LAYER IS EXPECTED

STRENGTHEN TO ABOUT 35 KTS LATER THIS MORNING AS UPSTREAM UPR TROUGH

NOW OVER THE UPR GRT LKS FURTHER AMPLIFIES SEWD.  COUPLED WITH

RESIDUAL EML PLUME...SETUP MAY ONCE AGAIN YIELD SPORADIC DMGG WIND

GUSTS AND PERHAPS MARGINALLY SVR HAIL AS THE STORM CLUSTER CONTINUES

E OR ENEWD.



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 26035.





...CORFIDI

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