

649 

WWUS20 KWNS 292327

SEL4

SPC WW 292327

ARZ000-LAZ000-MSZ000-300700-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 74

NWS STORM PREDICTION CENTER NORMAN OK

625 PM CDT TUE MAR 29 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       SOUTHEAST ARKANSAS

       NORTHERN LOUISIANA

       NORTHERN AND CENTRAL MISSISSIPPI



EFFECTIVE THIS TUESDAY NIGHT AND WEDNESDAY MORNING FROM 625 PM

UNTIL 200 AM CDT.



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 55

STATUTE MILES NORTH AND SOUTH OF A LINE FROM 45 MILES NORTHWEST

OF NATCHITOCHES LOUISIANA TO 35 MILES NORTH NORTHEAST OF MERIDIAN

MISSISSIPPI.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).



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 72...WW 73...



DISCUSSION...ELEVATED TSTMS ARE EXPECTED TO INCREASE IN COVERAGE AND

INTENSITY THIS EVENING IN ADVANCE OF POTENT SHORT-WAVE TROUGH

TRANSLATING ESEWD THROUGH KS/OK.  INCREASING LOW-LEVEL WARM THERMAL

AND MOISTURE ADVECTION BENEATH A STEEP MIDLEVEL LAPSE RATE PLUME

WILL RESULT IN SUFFICIENT INSTABILITY FOR VIGOROUS UPDRAFT GROWTH.

WHEN COUPLED WITH 40-45 KT OF EFFECTIVE BULK SHEAR...ENVIRONMENT

WILL BE SUPPORTIVE OF PERIODIC SUPERCELL STRUCTURES WITH THE MAIN

THREAT BEING LARGE HAIL.



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 500. MEAN STORM

MOTION VECTOR 24025.





...MEAD

