WATCHES: Tornado Watch Number 139

WWUS20 KWNS 140642
SEL9
SPC WW 140642
ARZ000-LAZ000-MSZ000-TXZ000-141300-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 139
NWS STORM PREDICTION CENTER NORMAN OK
140 AM CDT SAT APR 14 2007

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

EXTREME SOUTHEAST ARKANSAS
CENTRAL AND NORTHEAST LOUISIANA
EXTREME WEST CENTRAL MISSISSIPPI
EXTREME SOUTHEAST TEXAS

EFFECTIVE THIS SATURDAY MORNING FROM 140 AM UNTIL 800 AM CDT.

TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND
GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE
AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 70 STATUTE
MILES EAST AND WEST OF A LINE FROM 50 MILES NORTHEAST OF MONROE
LOUISIANA TO 50 MILES SOUTH OF FORT POLK LOUISIANA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE
UPDATE (WOUS64 KWNS WOU9).

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.

OTHER WATCH INFORMATION...THIS TORNADO WATCH REPLACES TORNADO
WATCH NUMBER 136...SEVERE THUNDERSTORM WATCH NUMBER 137. WATCH
NUMBER 136 137 WILL NOT BE IN EFFECT AFTER 140 AM CDT.
CONTINUE...WW 138...

DISCUSSION...THUNDERSTORMS HAVE EVOLVED INTO A NE-SW ORIENTED LINE
FROM NRN LA INTO SE TX. THIS BAND OF CONVECTION WILL PERSIST
THROUGH THE MORNING HOURS AND MOVE EWD IN CONJUNCTION WITH A SURFACE
WAVE ON THE FRONT ACROSS NRN LA/SE AR. MID-UPPER 60S BOUNDARY LAYER
DEWPOINTS ACROSS LA WILL CONTRIBUTE TO NEAR SURFACE-BASED
INSTABILITY...AND SOME DESTABILIZATION IS EXPECTED NEAR THE MS RIVER
LATER THIS MORNING. VERTICAL SHEAR WILL REMAIN SUFFICIENTLY STRONG
FOR EMBEDDED SUPERCELLS WITH AN ASSOCIATED RISK FOR A COUPLE OF
TORNADOES...AS WELL AS THE POTENTIAL FOR DAMAGING WINDS/HAIL WITH
BOWING STRUCTURES IN THE LINE.

AVIATION...TORNADOES AND 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 24040.

..THOMPSON

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