STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 031300Z - 041200Z THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS NE TX...EXTREME SRN AR...NRN LA...CENTRAL/SRN MS...SRN AL...NWRN FL PANHANDLE...TO THE RIGHT OF A LINE FROM 40 S LUL MCB ESF 40 SSE TYR 45 NW TYR PRX TXK 50 NNW MEI 0A8 30 ENE TOI MAI CEW 40 S LUL. THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE TO THE RIGHT OF A LINE FROM 25 S GPT CLL SJT 55 NE BGS LBL AKO 81V 70 SSE GDV DIK 40 SW BIS MBG MHE 45 WSW SPW 40 SW FOD P35 30 SSE OJC 45 NNW FYV FSM HOT GLH GWO CBM BHM ATL AND CLT SOP 25 S ILM ...CONT... MLB PIE. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 40 NW ELO MSP CID BLV PAH 40 WSW BNA CSV HTS PKB 35 NW EKN SHD RIC 45 NE ORF ...CONT... 40 E PSX VCT 70 W COT. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM CEC 35 S PDT PUW 85 WNW FCA. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 40 ESE P07 BGS AMA AKO 30 WSW BFF 25 NE DGW 55 N CPR RIW 45 E EVW 4HV PGA 25 NNW PRC EED DAG BFL VBG. --- SYNOPSIS --- PROGRESSIVE UPPER AIR PATTERN WILL CONTINUE DAY-1...FEATURING AMPLIFYING WRN CONUS LONGWAVE TROUGH. ASSOCIATED CYCLONE NOW MOVING ONSHORE NRN CA. PLACEMENT/TIMING OF ITS LANDFALL WERE GENERALLY WELL FORECAST BY LAST 24-36 HOURS OF ETA AND SPECTRAL PROGS...FOMENTING RELATIVELY STRONG CONFIDENCE IN MODEL FCST OF THIS FEATURE TO N-CENTRAL HIGH PLAINS AND SRN ROCKIES AS POSITIVELY TILTED/OPEN-WAVE TROUGH BY END OF PERIOD. SHORTWAVE TROUGH -- NOW EVIDENT ON MOISTURE CHANNEL IMAGERY FROM SRN WI/NRN IL VORTICITY MAX SWD THROUGH IL -- IS FORECAST TO MOVE EWD ACROSS S-CENTRAL GREAT LAKES AND LOWER OH VALLEY REGION DURING DAY...REACHING WRN MD/VA/CAROLINAS BY 04/12Z. BOTH THIS FEATURE AND UPSTREAM SHORTWAVE RIDGE SHOULD AMPLIFY THROUGHOUT TODAY INTO THIS EVENING. AT SURFACE...WAVY FRONTAL ZONE IS INTERTWINED WITH SEVERAL CONVECTIVE OUTFLOWS FROM OFFSHORE NERN FL ACROSS CENTRAL FL...THEN NWWD TOWARD MESOLOW OVER ERN MS/WRN AL...ACROSS NRN LA NEAR SHV...THEN WSWWD AND WWD ACROSS CENTRAL TX TO NEAR SJT AND MAF. EXPECT NWD RETREAT OF WRN PORTION OF FRONT THIS AFTERNOON TOWARD RED RIVER...AND PERHAPS INTO ERN TX PANHANDLE/SWRN OK BY 04/00Z. FRONT MAY ALSO RETREAT NWD SOMEWHAT ACROSS CENTRAL/NRN FL AND FL PANHANDLE BEFORE ARRIVAL OF CLOUD/PRECIP SHIELD GENERATED BY ONGOING MCS. FARTHER NW...INTENSE LEE-SIDE CYCLOGENESIS WILL OCCUR OVER ERN CO THIS AFTERNOON -- ALONG TROUGH EXTENDING FROM ERN MT TO W TX. RESULTANT LOW WILL DEEPEN FURTHER AS IT MOVES ACROSS SWRN NEB/NWRN KS REGION TONIGHT. --- ARKLATEX REGION TO GA/NRN FL --- MCS NOW MOVING SEWD ACROSS ERN MS/WRN AL MAY CONTINUE TO PRESENT INTERMITTENT SEVERE HAIL/GUST THREAT AS IT CROSSES PORTIONS CENTRAL/SRN AL NEXT SEVERAL HOURS. ADDITIONAL DEVELOPMENT/ INTENSIFICATION POSSIBLE WITH REMNANTS OF THIS ACTIVITY IN ASSOCIATED VERTICAL SCENT FIELD THIS AFTERNOON OVER SERN AL/SRN GA. OTHERWISE...SCATTERED TO NUMEROUS TSTMS EXPECTED TO DEVELOP LATE MORNING THROUGH LATE AFTERNOON ALONG AND WITHIN 100-200 NM S OF FRONT AND MCS OUTFLOW ACROSS REGION...MAIN SEVERE THREATS BEING LARGE HAIL AND DAMAGING GUSTS. DENSE COVERAGE OF SEVERE HAIL/WIND EVENTS IS ANTICIPATED WITHIN MDT RISK AREA. CAP SHOULD WEAKEN WITH EWD EXTENT ALONG AND S OF OUTFLOW-MODULATED FRONTAL ZONE. CAPPING ALSO SHOULD WEAKEN THROUGHOUT 15Z-21Z TIME FRAME AMIDST DIABATIC SURFACE HEATING AND LIFT ALONG FRONTAL/OUTFLOW BOUNDARIES...WHERE GREAT MAJORITY OF TSTMS SHOULD INITIATE. 7-8 DEG C/KM MIDLEVEL LAPSE RATES AND SURFACE DEW POINTS UPPER 60S TO LOW 70S F WILL SUPPORT AFTERNOON MLCAPE 2000-3500 J/KG. WEAK LOW-MIDLEVEL FLOW EXPECTED ACROSS REGION WITH ENVIRONMENTAL VERTICAL WIND PROFILE BEING NEARLY UNIDIRECTIONAL FROM ROUGHLY WNW DIRECTION. --- SRN PLAINS --- SOMEWHAT MORE EXPLOSIVE...BUT ALSO MORE CONDITIONAL...CONVECTIVE POTENTIAL IS FARTHER W ALONG REMAINS OF WARM FRONT AND NEARBY DRYLINE. BY MID-LATE AFTERNOON...NRN PERIPHERY OF MID-UPPER 60S SURFACE DEW POINTS...STRENGTHENING MID-UPPER LEVEL FLOW AND BACKED SFC WINDS WILL YIELD QUITE FAVORABLE COMBINATION OF SHEAR/INSTABILITY FOR ALL MODES OF SEVERE...GIVEN CAP BREAKAGE. LATE APPROACH OF SHORTWAVE TROUGH -- WITH SHORTWAVE RIDGE STILL NEARLY OVERHEAD AT 21Z -- AND PREVALENCE OF STRONG CAPPING SUGGEST THAT TSTMS INITIATING NEAR DRYLINE SHOULD REMAIN RELATIVELY WELL- SEPARATED AND DISCRETE...AND THAT INITIATION MAY WAIT UNTIL LATE AFTERNOON/EARLY EVENING. PRIMARY UNCERTAINTY FOR THIS FCST IS NRN REACH OF VERY MOIST AIR MASS NOW ALONG AND S OF AFOREMENTIONED WARM FRONT. FRONT MAY BECOME MORE DIFFUSE ON ITS WRN END THIS AFTERNOON AMIDST STRONG LOW LEVEL SELYS PER ETA PROGS...ALLOWING NARROW PLUME OF RICH MOISTURE TO ADVECT NWWD ACROSS ERN TX PANHANDLE/WRN OK. HOWEVER...CURRENT TRENDS SUGGEST SHARPER NEAR-FRONT THETAE GRADIENT SHOULD BE MAINTAINED AND INTERSECT DRYLINE SOMEPLACE BETWEEN ABI E- CENTRAL TX PANHANDLE...HENCE MAXIMIZED CONDITIONAL SEVERE PROBABILITIES THAT REGION. --- CENTRAL PLAINS --- STRONG CAPPING SHOULD MINIMIZE CONVECTIVE DEVELOPMENT ALONG DRYLINE FROM SW NEB THROUGH KS INTO NWRN OK DURING DAYLIGHT HOURS...ALTHOUGH GIVEN INCREASING VERTICAL SHEAR FROM LATE AFTERNOON ONWARD...ANY TSTMS WHICH DO DEVELOP WILL ROTATE WITH POTENTIAL FOR DAMAGING WIND/HAIL. CONVECTION WOULD BE RELATIVELY HIGH BASED GIVEN UPPER 40S TO LOW 50S F SURFACE DEW POINTS OVER MUCH OF AREA...YIELDING LARGE DEW POINT DEPRESSIONS AND INVERTED-V THERMODYNAMIC PROFILES IN BOUNDARY LAYER. MOST CONVECTION AND SEVERE POTENTIAL OVER THIS REGION SHOULD BE AFTER 00Z OVER NEB...WHEN ISOLATED TO WIDELY SCATTERED DIURNAL CONVECTION EXPANDS/EVOLVES NOCTURNALLY INTO MCS WITH POTENTIAL FOR ENHANCED CORRIDOR OF HAIL/WIND EVENTS. CYCLOGENESIS WILL OCCUR WITH INTENSE LOW LEVEL WAA...MOIST ADVECTION AND RELATED DESTABILIZATION ANTICIPATED JUST E-NE OF DEEPENING SFC LOW. PLUMES OF INCREASINGLY MOIST...ELEVATED LOW LEVEL PARCELS WILL BE ISENTROPICALLY RAISED TO LFC...YIELDING SCATTERED TO LOCALLY NUMEROUS TSTMS AFTER 04Z IN REGIME OF STEEP LAPSE RATES. 1000-2000 J/KG ELEVATED MUCAPE POSSIBLE WITH DEEP-LAYER SHEAR SUFFICIENT TO SUPPORT ELEVATED SUPERCELLS AND BOWS. --- NERN AL/NRN GA TO CENTRAL APPALACHIANS --- BOUNDARY LAYER INSTABILITY EXPECTED TO DECREASE GENERALLY WITH NWD EXTENT ACROSS REGION INTO VA/WV/ERN KY MOUNTAINS...WHILE COLD DAMMING REGIME FARTHER E NARROWS SURFACE-BASED WARM SECTOR. HOWEVER...EXPECT SUFFICIENT LOW LEVEL THETAE TO BECOME JUXTAPOSED WITH MIDLEVEL COOLING/DESTABILIZATION AHEAD OF APPROACHING TROUGH ALOFT FOR WIDELY SCATTERED TSTMS BY MID/LATE AFTERNOON...A FEW OF WHICH MAY PRODUCE HAIL/GUSTS NEAR SEVERE LEVELS. THOUGH LOW LEVEL CONVERGENCE SHOULD BE WEAK WITH STRONG WLY COMPONENT TO FLOW...WEAK CAPPING SHOULD PERMIT ENOUGH CONVECTIVE DEVELOPMENT -- IN ENVIRONMENT OF INCREASING DEEP-LAYER SPEED SHEAR -- FOR RISK OF ORGANIZED SEVERE WIND/HAIL. ..EDWARDS.. 05/03/03