

139 

WWUS20 KWNS 191920

SEL5

SPC WW 191920

ARZ000-OKZ000-TXZ000-200300-



URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 155

NWS STORM PREDICTION CENTER NORMAN OK

220 PM CDT TUE APR 19 2011



THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF



       WESTERN ARKANSAS

       EASTERN OKLAHOMA

       NORTH-CENTRAL AND NORTHEAST TEXAS



EFFECTIVE THIS TUESDAY AFTERNOON AND EVENING FROM 220 PM UNTIL

1000 PM CDT.



TORNADOES...HAIL TO 4 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.



THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 85 STATUTE

MILES EAST AND WEST OF A LINE FROM 15 MILES NORTH OF HARRISON

ARKANSAS TO 60 MILES EAST SOUTHEAST OF DALLAS TEXAS.  FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU5).



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 154...



DISCUSSION...EXPLOSIVE TSTM DEVELOPMENT IS EXPECTED ALONG COLD FRONT

THIS AFTERNOON AS IT ENCOUNTERS A STRONGLY UNSTABLE AIR MASS WITH

MLCAPE APPROACHING 3000-4500 J/KG.  DEEP-LAYER SHEAR VECTORS

ORIENTED AT AN ANGLE TO THE FRONT IS SUGGESTIVE OF SUPERCELL

EVOLUTION GIVEN THE DEGREE OF INSTABILITY AND 40-50 KT SWLY MIDLEVEL

WIND FIELD.  VERY LARGE HAIL /I.E. GREATER THAN BASEBALL SIZE/ WILL

BE POSSIBLE IN ADDITION TO A RISK OF A FEW TORNADOES GIVEN EFFECTIVE

SRH VALUES OF 150-300 M2/S2.



AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 4 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 60 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

600. MEAN STORM MOTION VECTOR 25030.





...MEAD

