

217 

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

