

697 

WWUS20 KWNS 092350

SEL8

SPC WW 092350

ARZ000-LAZ000-MSZ000-TXZ000-100600-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 678

NWS STORM PREDICTION CENTER NORMAN OK

550 PM CST SUN DEC 9 2012



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHERN ARKANSAS

       WESTERN AND NORTHERN LOUISIANA

       EXTREME WESTERN MISSISSIPPI

       SOUTHEAST TEXAS



EFFECTIVE THIS SUNDAY AFTERNOON FROM 550 PM UNTIL MIDNIGHT CST.



HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 90

STATUTE MILES EAST AND WEST OF A LINE FROM 30 MILES NORTH

NORTHWEST OF MONTICELLO ARKANSAS TO 45 MILES SOUTHEAST OF

HUNTSVILLE TEXAS.  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 677...



DISCUSSION...SCATTERED TSTMS NEAR FRONT...AS WELL AS CLUSTERED

CONVECTION TO ITS E...SHOULD POSE RISK FOR SVR HAIL AND DAMAGING

GUSTS THROUGH EVENING.  MRGL SUPERCELL SCENARIO EXISTS FOR

DISCRETE/PREFRONTAL CONVECTION...WITH 45-55 KT EFFECTIVE SHEAR

MAGNITUDES BUT WEAK NEAR-SFC WINDS.  EFFECTIVELY SFC-BASED PARCELS

SHOULD PERSIST THROUGH ABOUT 06Z OVER MUCH OF AREA AS LONG AS

WARM/MOIST ADVECTION OFFSETS DIABATIC SFC COOLING.  TSTMS NEAR FRONT

SHOULD BE UNDERCUT QUICKLY...PER SPC MESOSCALE DISCUSSION 2141.



AVIATION...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 450. MEAN STORM

MOTION VECTOR 23035.





...EDWARDS

