

134 

WWUS20 KWNS 111457

SEL0

SPC WW 111457

NYZ000-LOZ000-112200-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 570

NWS STORM PREDICTION CENTER NORMAN OK

1100 AM EDT SAT JUL 11 2009



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN...CENTRAL...AND UPSTATE NEW YORK

       LAKE ONTARIO



EFFECTIVE THIS SATURDAY MORNING AND EVENING FROM 1100 AM 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 75

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

SARANAC LAKE NEW YORK TO 35 MILES WEST SOUTHWEST OF ELMIRA NEW

YORK.  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.



DISCUSSION...A BROKEN BAND OF PRE-FRONTAL THUNDERSTORMS WILL

PROGRESS EWD FROM WRN INTO CENTRAL NY THROUGH THE AFTERNOON.  A

RELATIVELY NARROW CORRIDOR OF WEAK-MODERATE INSTABILITY IS

DEVELOPING AHEAD OF THIS CONVECTION...AND LOW-MID LEVEL FLOW WILL

GRADUALLY INCREASE WITH THE APPROACH OF A SHORTWAVE TROUGH FROM THE

UPPER GREAT LAKES.  THE COMBINATION OF INSTABILITY AND VERTICAL

SHEAR APPEARS SUFFICIENT FOR A FEW STORMS WITH DAMAGING WINDS AND

MARGINALLY SEVERE HAIL THROUGH THE AFTERNOON.



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 26030.





...THOMPSON

