WATCHES: Tornado Watch Number 563

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URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 563
NWS STORM PREDICTION CENTER NORMAN OK
220 PM MDT WED JUL 8 2009

THE NWS STORM PREDICTION CENTER HAS ISSUED A
TORNADO WATCH FOR PORTIONS OF

EXTREME EASTERN MONTANA
WESTERN NORTH DAKOTA
WESTERN SOUTH DAKOTA
NORTHEAST WYOMING

EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 220 PM UNTIL
1000 PM MDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 100 STATUTE
MILES EAST AND WEST OF A LINE FROM 55 MILES EAST NORTHEAST OF
WILLISTON NORTH DAKOTA TO 35 MILES SOUTH SOUTHWEST OF RAPID CITY
SOUTH DAKOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU3).

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR
TORNADOES AND 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.

DISCUSSION...THUNDERSTORMS ARE EXPECTED TO DEVELOP AND INTENSIFY
ALONG FRONTAL BOUNDARY OVER EXTREME ERN MT AND NERN WY DURING THE
NEXT 1-2 HRS. AIR MASS HAS DESTABILIZED THIS AFTERNOON WITH MLCAPE
OF 1000-1500 J/KG AS STRONG HEATING TAKES PLACE SOUTH OF EARLIER
CONVECTION OVER NERN MT AND NWRN ND. DYNAMIC FORCING FOR LARGE
SCALE ASCENT WILL INCREASE THROUGH THE EVENING HAS A SHORT WAVE
TROUGH PROGRESSES ENEWD ACROSS MT...IN CONJUNCTION WITH A VERY
STRONG MID/UPPER LEVEL JET STREAK. THIS IS CONTRIBUTING TO 40-50 KT
DEEP LAYER SHEAR SUPPORTIVE OF SUPERCELLS...WHILE STRENGTHENING LOW
LEVEL JET AND VEERING PROFILES IN LOWEST 2-3 KM INDICATE POTENTIAL
FOR A FEW TORNADOES WITH INITIAL STORM DEVELOPMENT. STORMS ARE
EXPECTED TO GROW UPSCALE BY THE EVENING HOURS WITH A
FORWARD-PROPAGATING LINEAR MCS MOVING ACROSS WRN ND AND PARTS OF WRN
SD AND INCREASING THREAT FOR MORE WIDESPREAD WIND DAMAGE.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 26035.

...WEISS

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