WWUS20 KWNS 220217
SEL7
SPC WW 220217
ALZ000-KYZ000-TNZ000-220800-

URGENT - IMMEDIATE BROADCAST REQUESTED
TORNADO WATCH NUMBER 587
NWS STORM PREDICTION CENTER NORMAN OK
820 PM CST SAT DEC 21 2013

THE NWS STORM PREDICTION CENTER HAS ISSUED A

* TORNADO WATCH FOR PORTIONS OF 
  WESTERN AND NORTHERN ALABAMA
  SOUTH CENTRAL KENTUCKY
  MIDDLE TENNESSEE

* EFFECTIVE THIS SATURDAY NIGHT AND SUNDAY MORNING FROM 820 PM
  UNTIL 200 AM CST.

* PRIMARY THREATS INCLUDE...
  SEVERAL TORNADOES POSSIBLE
  SEVERAL DAMAGING WIND GUSTS TO 70 MPH LIKELY

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 55 STATUTE
MILES EAST AND WEST OF A LINE FROM 75 MILES EAST NORTHEAST OF
BOWLING GREEN KENTUCKY TO 40 MILES SOUTHEAST OF COLUMBUS
MISSISSIPPI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE
ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU7).

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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...CONTINUE...WW 583...WW 584...WW
585...WW 586...

DISCUSSION...A WELL-FORMED SQUALL LINE WILL MOVE EWD OVERNIGHT FROM
WRN TN/KY AND NRN MS INTO NW AL...MIDDLE TN AND CENTRAL KY. 
LOW-LEVEL MOISTURE ADVECTION AND MIXING WILL HELP MAINTAIN A
RELATIVELY WARM AND MOIST BOUNDARY LAYER WITH SURFACE-BASED
INSTABILITY AHEAD OF THE SQUALL LINE...WHILE VERTICAL SHEAR WILL
REMAIN STRONG FOR THE NEXT SEVERAL HOURS.  A COUPLE OF TORNADOES
WILL BE POSSIBLE WITH EMBEDDED CIRCULATIONS...WHILE DAMAGING WINDS
WILL BE THE PRIMARY THREAT.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL
SURFACE AND ALOFT TO 0.5 INCH. EXTREME TURBULENCE AND SURFACE
WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO
450. MEAN STORM MOTION VECTOR 24050.


...THOMPSON