DAY 2 CONVECTIVE OUTLOOK NWS STORM PREDICTION CENTER NORMAN OK 0242 AM CDT THU APR 08 2004 VALID 091200Z - 101200Z THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 55 SSW LTS 20 NW LTS 30 E CSM 50 NW MLC 35 SE PGO 10 N SHV 35 NE LFK 50 SW LFK 30 ESE AUS 45 ESE JCT 45 ENE ABI 55 SSW LTS. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 10 WNW SRQ MLB. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 35 NE CRP 10 NNW LRD ...CONT... 45 NW DRT 30 SSW SJT 55 NW ABI 10 WNW LBB 35 W ALM 50 SSE PHX 40 SSE EED 35 NE IGM 55 E INW 35 NNW CEZ 55 ESE SLC 50 ENE EVW 20 SSE RWL 30 WNW LIC 10 NNE DDC 35 WSW CNU 40 SSW TBN 30 NW DYR 35 E TUP 55 NW MEI 25 WNW HEZ 40 SSE LCH. ...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS OF SRN OK AND NRN/CENTRAL TX... ...SYNOPSIS... ETA...ETAKF...AND GFS ARE SIMILAR IN OVERALL SPEED AND LOCATION OF UPPER LOW NOW OVER AZ AS IT SHEARS EWD ACROSS THE SRN PLAINS FRIDAY. APPEARS OVERALL PATTERN WILL EVOLVE INTO A BROAD MID/UPPER LEVEL TROUGH WITH MODERATE WLY FLOW ALOFT FROM THE SRN ROCKIES EWD...SOUTH OF AN UPPER LOW OVER THE NRN PLAINS. PRIMARY DIFFERENCES BETWEEN THE MODELS REVOLVE AROUND THEIR SURFACE LOW/FRONTAL POSITIONS AND DEGREE OF BOUNDARY LAYER MOISTURE WITHIN DEVELOPING WARM SECTOR FRIDAY AFTERNOON. SHORT-RANGE ENSEMBLES APPEAR TO FAVOR A LOW CENTER OVER SWRN OK/FAR NWRN TX WITH AN E-W ORIENTED COLD FRONT MOVING STEADILY SWD ACROSS THE OH RIVER VALLEY AND INTO NRN OK/TX PANHANDLE BY LATE FRIDAY AFTERNOON...NEARER THE ETA SOLUTION. A DRY LINE IS ALSO EXPECTED TO BECOME ESTABLISHED FROM THE LOW CENTER SWD ACROSS CENTRAL TX TO JUST EAST OF THE BIG BEND BY LATE IN THE DAY. IN ADDITION...IT APPEARS SURFACE COLD FRONT NOW EXTENDING FROM THE SOUTHEAST INTO THE LOWER MS RIVER VALLEY WILL STALL ACROSS NRN FL AND THE NERN GULF COAST REGION EARLY IN THE PERIOD. THIS FEATURE WILL BECOME MORE DIFFUSE AS WRN END LIFTS NWD AS A WARM FRONT INTO SRN AR/CENTRAL MS DURING THE AFTERNOON/OVERNIGHT...AHEAD OF SURFACE LOW EXPECTED TO TRACK EWD INTO THE ARKLATEX REGION BY THE END OF THE PERIOD. ...SRN PLAINS... CLUSTER OR CLUSTERS OF ELEVATED CONVECTION SHOULD BE ONGOING OVER NWRN TX/WRN HALF OF OK FRIDAY MORNING WHICH WILL SHIFT STEADILY ENEWD THROUGH THE DAY. THOUGH ISOLATED LARGE HAIL MAY ACCOMPANY THIS ACTIVITY...APPEARS INSTABILITY AHEAD OF IT WILL REMAIN WEAK AND LIMIT OVERALL SEVERE THREAT WITH THESE STORMS. PRIMARY SEVERE THREAT SHOULD DEVELOP NEARER THE LOW CENTER/TRIPLE POINT AND ALONG THE DRY LINE INTO CENTRAL TX NEARER 21Z...IN WAKE OF THE EARLIER ACTIVITY ACCORDING TO THE ETA. EXPECT THUNDERSTORMS WILL INITIATE AND QUICKLY BECOME SEVERE FROM SRN OK INTO CENTRAL TX...WITH SEVERE THREAT BEING SUSTAINED EWD INTO THE EARLY TO MID EVENING AS STORMS SPREAD EAST AND POSSIBLY DEVELOP SSW ALONG DRY LINE. AS ACTIVITY SHIFTS EAST AND BOUNDARY LAYER COOLS... STORMS WILL BECOME MORE ELEVATED AND SEVERE THREAT MAY SLOWLY DIMINISH LATER IN THE EVENING/OVERNIGHT. ALTHOUGH SREF DATA FAVORS ETA SURFACE FRONT/LOW POSITIONS... APPEARS ETA MAY BE TOO DRY IN ITS BOUNDARY LAYER FORECASTS JUST EAST OF THE DRY LINE FRIDAY AFTERNOON...WITH LOWER 70F SURFACE DEW POINTS ALREADY ESTABLISHED OVER THE WRN GULF AND THE CENTRAL TX COAST. /GFS BRINGS UPPER 60F SURFACE DEW POINTS INTO N-CENTRAL TX DURING THE DAY./ MODIFIED ETA FORECAST SOUNDINGS ACROSS N-CENTRAL TX USING SURFACE DEW POINTS IN THE LOWER 60S INDICATE AT LEAST MODERATE INSTABILITY...ML CAPES FROM 1500-2000 J/KG...FROM SRN OK SWD INTO NWRN/N-CENTRAL TX WITH VERY LITTLE INHIBITION BY 21Z. IN ADDITION...FORECAST HODOGRAPHS ARE VERY FAVORABLE FOR LONG-LIVED SUPERCELLS WITH SUBSTANTIAL LOW LEVEL VEERING AND STEADILY INCREASING WLY WINDS THROUGH THE UPPER LEVELS SUPPORTING LONG HODOGRAPH LENGTHS. THUS...GIVEN DEGREE OF INSTABILITY AND VERY STEEP LAPSE RATES...A THREAT OF AT LEAST VERY LARGE HAIL WILL ACCOMPANY ANY SUSTAINED UPDRAFTS. SHOULD LOW LEVEL MOISTURE INCREASE OVER WHAT IS NOW FORECAST BY THE ETA...LOWER LCLS WILL ENHANCE THE POTENTIAL FOR PERSISTENT TORNADOES...AND OUTLOOK MAY NEED TO BE UPGRADED TO A MODERATE IN LATER FORECASTS. FOR NOW...GIVEN UNCERTAINTY REGARDING AMOUNT OF BOUNDARY LAYER MOISTURE AND EFFECTS/LOCATION OF MORNING CONVECTION...WILL OPT TO KEEP A SLIGHT RISK WITH INCLUSION OF A SIGNIFICANT SEVERE AREA AND HIGHER PROBABILITIES ALONG NRN PORTION OF DRY LINE. ..EVANS.. 04/08/2004