

704 

WWUS20 KWNS 260354

SEL1

SPC WW 260354

ARZ000-LAZ000-OKZ000-TXZ000-261100-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 61

NWS STORM PREDICTION CENTER NORMAN OK

1050 PM CDT FRI MAR 25 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       WESTERN ARKANSAS

       NORTHWEST LOUISIANA

       SOUTH-CENTRAL AND SOUTHEAST OKLAHOMA

       NORTHEAST TEXAS



EFFECTIVE THIS FRIDAY NIGHT AND SATURDAY MORNING FROM 1050 PM

UNTIL 600 AM CDT.



HAIL TO 2 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 70

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

OF DURANT OKLAHOMA TO 50 MILES EAST OF TEXARKANA ARKANSAS.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU1).



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.



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

INTENSITY OVERNIGHT TO THE N OF QUASI-STATIONARY BOUNDARY EXTENDING

FROM SFC LOW OVER N-CNTRL TX ESEWD INTO NRN LA.  THE COMBINATION OF

STEEP MIDLEVEL LAPSE RATES AND INCREASING LOW-LEVEL MOISTURE ARE

YIELDING A MODERATELY UNSTABLE AIR MASS WITH MUCAPE OF 1000-2000

J/KG.

CURRENT THINKING IS THAT NOCTURNAL COOLING IN THE BOUNDARY LAYER AND

MODEST MOISTURE CONTENT WILL RESULT IN SUFFICIENT SURFACE-BASED

CONVECTIVE INHIBITION SUCH THAT STORMS SHOULD REMAIN SLIGHTLY

ELEVATED.  GIVEN THE PRESENCE OF 40-50 KT OF EFFECTIVE BULK

SHEAR...ENVIRONMENT WILL BE SUPPORTIVE OF SUPERCELLS.  WHILE A BRIEF

TORNADO IS POSSIBLE...HAIL APPEARS TO BE THE PRIMARY HAZARD.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 500. MEAN STORM

MOTION VECTOR 27035.





...MEAD

