WATCHES: Tornado Watch Number 490

WWUS20 KWNS 072050
SEL0
SPC WW 072050
ALZ000-080100-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 490
NWS STORM PREDICTION CENTER NORMAN OK
350 PM CDT SAT JUL 7 2007

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

EAST CENTRAL ALABAMA

EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 350 PM UNTIL
800 PM CDT.

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 60 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 35 STATUTE
MILES NORTH AND SOUTH OF A LINE FROM 20 MILES SOUTH SOUTHEAST OF
AUBURN ALABAMA TO 30 MILES WEST OF MONTGOMERY ALABAMA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU0).

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...A MID LEVEL AND ASSOCIATED SURFACE LOW ARE MOVING EWD
FROM MS TO WRN AL. IN ADVANCE OF THIS SYSTEM...RAINFALL HAS
MAINTAINED AN E-W RAIN-COOLED BOUNDARY/WARM FRONT NEAR MGM.
LOW-LEVEL SHEAR /EFFECTIVE SRH OF 100-200 M2/S2/ IS MAXIMIZED ALONG
AND N OF THIS BOUNDARY PER THE BMX AND MXX VWP/S...AND DEEP LAYER
SHEAR IS AT LEAST MARGINALLY FAVORABLE FOR SUSTAINED SUPERCELLS
ALONG THIS SAME CORRIDOR. GIVEN THE MOIST LOW LEVELS AND MODERATE
INSTABILITY...STORMS INTERACTING WITH THE BOUNDARY MAY PRODUCE A
COUPLE OF TORNADOES FOR THE REMAINDER OF THE AFTERNOON AND INTO THIS
EVENING.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 50 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
500. MEAN STORM MOTION VECTOR 25020.

..THOMPSON

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