WATCHES: Severe Thunderstorm Watch Number 688

WWUS20 KWNS 200712
SEL8
SPC WW 200712
ARZ000-LAZ000-MSZ000-TNZ000-TXZ000-201300-

URGENT - IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 688
NWS STORM PREDICTION CENTER NORMAN OK
110 AM CST THU DEC 20 2012

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

EAST-CENTRAL AND SOUTHEASTERN ARKANSAS
NORTHERN AND CENTRAL LOUISIANA
WESTERN AND NORTHERN MISSISSIPPI
SMALL PART OF SOUTHWESTERN TENNESSEE
SMALL PART OF SOUTHEAST TEXAS

EFFECTIVE THIS THURSDAY MORNING FROM 110 AM UNTIL 700 AM CST.

HAIL TO 1 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 75
MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 95
STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES SOUTH
SOUTHWEST OF FORT POLK LOUISIANA TO 25 MILES NORTH NORTHWEST OF
MEMPHIS TENNESSEE. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU8).

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 686...WW 687...

DISCUSSION...STRONGLY FORCED SQUALL LINE IS FCST TO MOVE INTO AND
ACROSS WW AREA THROUGH REMAINDER PRE-DAWN HOURS...MAINTAINING
QUASI-LINEAR MODE AND OFFERING DAMAGING GUSTS AS PRIMARY/DOMINANT
RISK. STG DEEP-LAYER SHEAR AND POCKETS OF FAVORABLE EFFECTIVE SRH
INDICATE A BRIEF QLCS TORNADO MAY OCCUR. CORE REGION OF THREAT IS
CENTRAL LA TO SERN AR AND NWRN MS. DECREASE IN NEAR-SFC THETAE WITH
NWD EXTENT WILL RENDER THREAT MORE MRGL WITH TIME ACROSS WRN TN AND
NERN AR...WHILE SOME UNCERTAINTY REMAINS REGARDING EXTENT OF
BACKBUILDING COASTWARD OVER LA.

AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 1 INCH. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65 KNOTS.
A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM MOTION
VECTOR 25040.


...EDWARDS

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