Posted by JAC on 4/16/2009, 1:18 pm, in reply to "Severe weather South / Cntrl TX late tonight into Friday morning"

MESOSCALE DISCUSSION 0481 NWS STORM PREDICTION CENTER NORMAN OK 1120 AM CDT THU APR 16 2009 AREAS AFFECTED...PORTIONS NW TX...ERN/NRN TX PANHANDLE...CENTRAL/ERN OK PANHANDLE...WRN OK...WRN KS...EXTREME ERN CO. CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 161620Z - 161815Z POTENTIAL IS INCREASING FOR ISOLATED TO WIDELY SCATTERED AND MARGINAL SVR HAIL...WITHIN GROWING PLUME OF CONVECTION NOW EVIDENT FROM SW OK ACROSS NERN TX PANHANDLE TO VICINITY KS/CO BORDER. WHILE THIS ACTIVITY MOVES N WITH GRADUAL INTENSIFICATION...SOME BACKBUILDING/FILLING ALSO IS POSSIBLE ACROSS PORTIONS NW TX AND CENTRAL/NRN PANHANDLE. THIS IS SEPARATE FROM MID-LATE AFTERNOON/SFC-BASED SVR THREAT DISCUSSED IN DAY-1 OUTLOOK...AND IS NOT EXPECTED TO BE AS WELL-ORGANIZED. 12Z UPPER AIR ANALYZES AND RUC GUIDANCE INDICATE INCREASING LOW LEVEL MOISTURE -- ESPECIALLY IN 925-850 MB LAYER -- ASSOCIATED WITH BROAD/40-50KT SSELY LLJ. MAX MOISTURE TRANSPORT SHOULD CONTINUE ACROSS THIS REGION...PERHAPS SHIFTING SLIGHTLY WWD AS PANHANDLES/SWRN KS/SERN CO SEGMENT OF LLJ BACKS AND INTENSIFIES SOMEWHAT THROUGH EARLY AFTERNOON. THIS REGIME GRADUALLY WILL BECOME INCREASINGLY JUXTAPOSED WITH ERN EDGE OF MORE ROBUST LARGE-SCALE ASCENT AND COOLING ALOFT AS CENTER OF BROAD UPPER CYCLONE PIVOTS EWD THROUGH 4-CORNERS AREA. MODIFIED 12Z RAOBS AND RUC SOUNDINGS INDICATE ELEVATED MUCAPE IN 1000-1500 J/KG RANGE. PRIMARY LIMITING FACTOR APPEARS TO BE LACK OF MORE ROBUST SHEAR FOR ELEVATED LIFTED PARCELS. WITH STRONGEST DEEP-LAYER WINDS REMAINING W OF THIS AREA AT LEAST UNTIL EARLY-MID AFTERNOON...FCST SOUNDINGS SHOW ONLY SMALL CHANGES WITH HEIGHT IN DIRECTION/SPEED OF FLOW THROUGH INFLOW-BUOYANT LAYERS. THIS SHOULD KEEP EFFECTIVE SHEAR MAGNITUDES BELOW 30 KT IN MOST OF DISCUSSION AREA UNTIL INFLOW PARCELS BECOME SFC-BASED...LIKELY AROUND MID-AFTERNOON NEAR W EDGE OF THIS CLOUD/PRECIP AREA WHERE HEATING IS STRONGER. KINEMATIC GEOMETRY ALSO SHOULD CONTRIBUTE TOWARD MIXTURE OF MULTICELL CLUSTERS AND LINEAR MODAL TENDENCIES. ..EDWARDS.. 04/16/2009