MESOSCALE DISCUSSION 0273

MESOSCALE DISCUSSION 0273
NWS STORM PREDICTION CENTER NORMAN OK
0231 PM CDT SUN MAR 18 2012

AREAS AFFECTED...ERN OK/TX PANHANDLES...FAR WRN OK...WRN N TX

CONCERNING...SEVERE POTENTIAL...WATCH LIKELY

VALID 181931Z - 182130Z

THE SEVERE THREAT WILL INCREASE OVER THE NEXT 1-3 HOURS AND
THUNDERSTORMS ARE EXPECTED TO INITIATE AROUND 21Z. LARGE HAIL WILL
BE THE MAIN THREAT BUT A FEW TORNADOES WILL ALSO BE POSSIBLE. A WW
WILL LIKELY BE NEEDED WITHIN THE NEXT HOUR OR SO.

19Z VIS SAT IMAGERY SHOWED CUMULUS BEGINNING TO DEVELOP ACROSS THE
TX S PLAINS E OF LBB AHEAD OF A DRYLINE EXTENDING SWD FROM WRN KS
THROUGH SWRN TX. AS TEMPERATURES HAVE WARMED INTO THE MID AND UPPER
70S THIS AFTERNOON...ONLY WEAK MLCIN REMAINS WITH MLCAPE VALUES NOW
APPROACHING 2000 J/KG. WITH ADDITIONAL HEATING REMAINING CAP WILL
QUICKLY ERODE AND CONVECTIVE INITIATION IS EXPECTED WITHIN THE NEXT
COUPLE OF HOURS. WHILE THE MAIN UPPER LEVEL FORCING REMAINS WELL TO
THE WEST ACROSS AZ/NM WITH THE UPPER LEVEL TROUGH...HEIGHT FALLS
HAVE BEEN OCCURRING ACROSS THE REGION THIS AFTERNOON AND RECENT
PROFILER DATA HAVE INDICATED AN INCREASE IN MIDLEVEL FLOW STREAMING
INTO THE MCD AREA. GIVEN BULK SHEAR VALUES OF 35-45 KTS AND MIDLEVEL
LAPSE RATES AROUND 7.5 DEG C/KM...ORGANIZED SUPERCELL STORMS CAPABLE
OF LARGE HAIL ARE EXPECTED. WHILE LARGE HAIL WILL INITIALLY BE THE
MAIN THE THREAT...AS THE UPPER TROUGH MOVES EWD AND STRONGER DEEP
LAYER FORCING ENCROACHES UPON THE REGION TOWARD 00Z...LOW LEVEL
HODOGRAPHS WILL BECOME MORE FAVORABLE FOR TORNADO DEVELOPMENT.
THEREFORE...A TORNADO WATCH WILL LIKELY BE ISSUED.