SWODY1
SPC AC 200559
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1159 PM CST FRI FEB 19 2010
VALID 201200Z - 211200Z
...NO SVR TSTM AREAS FORECAST...
...SRN PLAINS...
AN UPPER-LEVEL LOW OFFSHORE FROM SRN CA WILL OPEN AND MOVE QUICKLY
EWD ACROSS THE FOUR CORNERS REGION TODAY AND INTO THE SRN PLAINS
TONIGHT. A PRONOUNCED 40 TO 50 KT LOW-LEVEL JET IS FORECAST TO
DEVELOP IN THE SRN PLAINS AHEAD OF THE SYSTEM THIS EVENING.
HOWEVER...LOW-LEVEL MOISTURE WILL NOT HAVE MUCH TIME TO RETURN NWD
INTO THE SRN PLAINS AND MODEL FORECASTS ONLY BRING SFC DEWPOINTS
INTO THE LOWER 50S F ACROSS NORTH TX BY LATE TONIGHT. IN SPITE OF
THE DRY BOUNDARY LAYER...MODEL FORECASTS ARE IN AGREEMENT INITIATING
SCATTERED THUNDERSTORMS AFTER MIDNIGHT IN WEST TX AND WRN OK
PRIMARILY DUE TO THE ELEVATED INSTABILITY AND STRONG LARGE-SCALE
ASCENT AHEAD OF THE APPROACHING UPPER-LEVEL TROUGH. THE ACTIVITY
SHOULD GRADUALLY SHIFT EWD ACROSS ECNTRL OK AND NORTH TX BY LATE IN
THE PERIOD AS THE LOW-LEVEL JET MOVES EWD. FORECAST SOUNDINGS AT 09Z
TO 12Z ALONG THE RED RIVER ONLY SHOW MUCAPE VALUES IN THE 300 TO 500
J/KG RANGE. HOWEVER...STEEP MID-LEVEL LAPSE RATES AND COLD AIR ALOFT
IN THE CORE OF THE UPPER-LEVEL TROUGH MAY COMPENSATE FOR THE WEAK
INSTABILITY ALLOWING A FEW OF THE STORMS TO HAVE A MARGINAL HAIL
POTENTIAL. ALTHOUGH MORE INSTABILITY MAY EXIST SWD ACROSS CNTRL
TX...WEAKER LARGE-SCALE ASCENT IN THE AREA SHOULD LIMIT CONVECTIVE
COVERAGE.
..BROYLES.. 02/20/2010
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