CONVECT> find swody1 CONVECT> mkc 12.4-3.5 ACUS1 KMKC 041223 SWODY1 MKC AC 041223 CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O. VALID 041300Z - 051200Z REF WW NUMBER 0206...VALID TIL 01600Z REF WW NUMBER 0207...VALID TIL 01600Z THERE IS A HIGH RISK OF SVR TSTMS OVER PORTIONS NERN TX...SERN OK...SWRN AR...AND NWRN LA...TO THE RIGHT OF A LINE FROM 50 NW POE 50 WNW LFK 55 ENE ACT 15 ENE DAL 25 S DUA 30 SSE MLC 15 S PGO 30 ESE HOT 10 S PBF 25 NE MLU 35 SW MLU 35 N POE 50 NW POE. SURROUNDING THE HIGH RISK...THERE IS A MDT RISK OF SVR TSTMS OVER ERN OK...MUCH OF AR...N-CENTRAL/NERN TX...NRN LA AND EXTREME NWR MS...TO THE RIGHT OF A LINE FROM 10 NNE POE 45 N CLL ACT 15 SW FTW 30 WSW ADM 45 ENE OKC 30 W BVO 10 E BVO 25 ENE FYV 35 SW ARG 25 WSW MEM 15 W GWO 30 N HEZ 10 WSW ESF 15 WSW ESF 10 NNE POE. OUTSIDE THE MDT AND HIGH RISKS...THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 25 NW LCH 30 S AUS 25 W HDO 40 ENE DRT 50 NNE DRT 20 SSE SJT 45 W END P28 45 ENE DDC 60 WSW HLC 40 SW MCK 20 E LBF 50 WSW YKN 30 E 3SE 20 E DBQ 25 SSE MMO 35 SSW HUF 15 SSE CKV 40 NE CBM 30 WNW LUL 30 NNE LFT 25 NW LCH. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 55 NNW ELO 15 ESE RHI 25 E SBN 40 ESE LUK 25 NNE TYS 30 SSE RMG 35 E BVE ...CONT... 40 SW GLS 55 NW LRD ...CONT... 20 WNW DRT 25 WSW LTS 35 ESE GAG 45 NE GAG 50 S DDC 25 WSW LBL 45 SW CAO 15 NW LVS 35 N 4SL 20 WSW MTJ 20 ENE VEL 50 E JAC 25 W COD 30 NE COD 25 W SHR 40 S SHR 30 ENE CPR 35 SE 4DG 25 NNW BFF 30 SSE CDR 50 SW PHP 45 N PHP 30 NE Y22 80 NE ISN. REGIONAL OUTBREAK OF TORNADIC SUPERCELLS POSSIBLE FROM N-CENTRAL TX EWD ACROSS NRN LA AND NEWD TOWARD OZARKS. SOME STRONG-VIOLENT TORNADOES POSSIBLE...ESPECIALLY INVOF HIGH RISK. --- SYNOPSIS --- VIGOROUS MIDDLE-UPPER LEVEL SHORTWAVE TROUGH -- NOW EVIDENT ON MOISTURE CHANNEL IMAGERY FROM 4-CORNERS CIRCULATION SEWD ACROSS ERN NM...IS FORECAST TO MOVE EWD THEN NEWD ACROSS SRN/CENTRAL PLAINS DURING PERIOD...WITH MIDDLE LEVEL LOW CENTERED OVER ERN NEB BY 05/12Z. ASSOCIATED DEEP LOW LEVEL CYCLONE IS DEVELOPING OVER WRN KS S OF NEB LOW -- SHOULD MOVE NEWD ACROSS KS TOWARD NW MO BY END OF PERIOD. NOCTURNAL WWD SLOSHING OF DRYLINE REVERSED BY 10Z THIS MORNING WITH GREATER INFLUENCE OF LARGE-SCALE FORCING...AND 35-40 KT WLYS OBSERVED ACROSS ERN NM/FAR W TX. THIS DRY SURGE SHOULD PROGRESS ENEWD ACROSS MUCH OF CENTRAL/NRN TX AND WRN OK DURING DAY...WITH SHARPENING DRYLINE SIMILAR TO 9Z RUC2 GUIDANCE. ...SEVERE THUNDERSTORM FORECAST DISCUSSION... --- SRN PLAINS TO LOWER MS VALLEY --- FOR MORE DETAILS REGARDING ONGOING/NOWCAST SEVERE WEATHER THREAT OVER TX/OK...REF WWS 206/207 AND THEIR STATUS REPORTS. ISALLOBARIC FORCING ASSOCIATED WITH CENTRAL PLAINS CYCLONE SHOULD RESULT IN STRONG LOW LEVEL WARM/MOIST ADVECTION ACROSS MUCH OF REGION THROUGHOUT THE DAY. THOUGH THIS SHOULD BE MITIGATED ON MESOSCALE BY CONVECTIVE OUTFLOWS...LARGE-SCALE FORCING IS STRONG ENOUGH SUCH THAT AIR MASSES SHOULD RECOVER QUICKLY BEHIND MOST MORNING/EARLY AFTERNOON CONVECTIVE CLUSTERS. DEEP LAYER OF RICH LOW LEVEL MOISTURE IN SHV RAOB. SURFACE DEW POINTS NOW IN 60S OVER REGION SHOULD INCREASE INTO UPPER 60S/LOW 70S..WHICH COMBINE WITH INSOLATION TO YIELD MLCAPE TO NEAR 3000 J/KG AND SBCAPE ABOVE 4000 J/KG. FORECAST SOUNDINGS AND MODIFIED 12Z RAOBS INDICATE BRN SHEAR AOA 100 J/KG LIKELY OVER MUCH OF AREA. ALSO...200-400 J/KG SR HELICITY AND NO NOTABLE LOW-MID LEVEL SR FLOW WEAKNESSES AOB 20 KT ALREADY OBSERVED IN FWD SOUNDING...AND SHOUDL REPRESENT MUCH OF HIGH RISK REGION TODAY. JUXTAPOSITION OF SEVERAL VERY FAVORABLE FORECAST PARAMETERS COMBINING TO INDICATE THREAT OF CYCLIC/TORNADIC SUPERCELLS. DEVELOPMENT EXPECTED IN SEVERAL AREAS -- INVOF DRYLINE...AHEAD OF DRYLINE IN ZONES OF MESOSCALE MASS CONVERGENCE...AND NEAR OUTFLOWS. IN ADDITION TO TORNADO THREAT... DAMAGING HAIL AND SEVERE GUSTS ARE ALSO LIKELY. SEVERE SQUALL LINE SHOULD EVOLVE FROM AFTERNOON/ EVENING SUPERCELLS AND MOVE EWD TOWARD MS RIVER BY END OF PERIOD. --- CENTRAL PLAINS...MID MS VALLEY --- LAPSE RATES EXPECTED TO BE FAVORABLY STEEP AS BAND OF LARGE-SCALE ASCENT NEAR AND N OF MID LEVEL CYCLONE PASSES OVER AREA THIS AFTERNOON. THUNDERSTORMS SHOULD DEVELOP BY MID AFTERNOON AND MOVE NEWD ACROSS REGION...PERHAPS IN AN ARC INVOF LEADING EDGE OF STRONGEST LOW LEVEL CONVERGENCE. LOW LEVEL THETAE ADVECTION MAY BE LIMITED BY LARGE AREA OF CONVECTION FARTHER S/SE...BUT SHOULD BE SUFFICIENT TO SUPPORT ISOLATED TO WIDELY SCATTERED SEVERE. VERTICAL SHEAR PROFILES ARE FORECAST TO BE GENERALLY UNIDIRECTIONAL....HOWEVER...SUFFICIENT SPEED SHEAR IS EXPECTED TO ENLARGE HODOGRAPHS AND SUPPORT A FEW ROTATING STORMS. LARGE HAIL AND A FEW TORNADOES POSSIBLE. SERN PORTION OF ARC MAY EVOLVE INTO A FEW BOW ECHOES THIS EVENING IF INFLOW IS NOT TOO RESTRICTED BY CONVECTION FARTHER SE...WITH SOME WIND DAMAGE THREAT. ..EDWARDS.. 05/04/99 ACUS1 KMKC 041650 SWODY1 MKC AC 041650 CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O. VALID 041630Z - 051200Z REF WW NUMBER 0208...VALID TIL 2100Z THERE IS A HIGH RISK OF SVR TSTMS OVER SERN AND EAST CENTRAL OK...MUCH OF WRN AND CENTRAL AR...NRN LA...AND NERN TX TO THE RIGHT OF A LINE FROM 30 S SHV 10 S TYR 25 E DAL DUA MLC 15 SE MKO FYV 45 S HRO 30 NE LIT 45 W GLH 35 SW MLU 30 S SHV. SURROUNDING THE HIGH RISK AREA...THERE IS A MDT RISK OF SVR TSTMS OVER THE REMAINDER OF ERN OK...N CENTRAL AND NERN TX...NRN AND CENTRAL LA...SRN MO...ERN AR...AND EXTREME WRN MS TO THE RIGHT OF A LINE FROM 10 NNE POE 45 N CLL ACT FTW ADM 55 NW MLC TUL SGF TBN 10 ESE P02 25 WSW MEM 15 W GWO 30 N HEZ 10 WSW ESF 15 WSW ESF 10 NNE POE. THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 25 NW LCH 30 S AUS 25 W HDO 40 ENE DRT 50 NNE DRT 10 E SJT ABI 20 E FSI P28 25 SW HLC MCK 20 E LBF 50 WSW YKN 30 E 3SE 20 E DBQ 25 SSE MMO 35 SSW HUF 15 SSE CKV 40 NE CBM 30 WNW LUL 30 NNE LFT 25 NW LCH. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 55 NNW ELO 15 ESE RHI 25 E SBN 40 ESE LUK 25 NNE TYS 30 SSE RMG 20 WSW PNS ...CONT... 40 ENE CRP 15 WNW LRD ...CONT... 20 WNW DRT 35 WSW ABI 20 WNW SPS FSI 25 WSW P28 LBL 35 NE CAO 25 SSW LHX 25 NNW LHX 10 WNW LIC 40 E FCL 40 E CYS 20 WSW BFF 20 W AIA 50 ESE CDR 25 S PHP 55 WSW Y26 45 WNW BIS 65 NW MOT. ...SEVERE THUNDERSTORM FORECAST DISCUSSION... ACTIVE SEVERE WEATHER EPISODE EXPECTED TO CONTINUE INTO TONIGHT AS VIGOROUS NEGATIVE TILT UPPER TROUGH MOVING INTO THE CENTRAL HIGH PLAINS LIFTS NEWD TOWARD THE LOWER/MIDDLE MO RIVER VALLEY TONIGHT. DEEP SURFACE LOW OVER SWRN KS IS FORECAST TO LIFT NEWD TOWARD S CENTRAL NEB THIS EVENING CONTINUING INTO ERN NEB TONIGHT. DRY LINE ARCING SWD FROM THE LOW ACROSS CENTRAL OK THEN SSWWD ACROSS TX IS MOVING EWD IN ADVANCE OF A COLD FRONT MOVING ACROSS SERN NM AND W TX. THE COLD FRONT MAY ACCELERATE AND MERGE WITH THE DRY LINE OVER PARTS OF CENTRAL TX TONIGHT...WITH THE EFFECTIVE COLD FRONT REACHING EXTREME ERN PARTS OF KS/OK/NERN THROUGH SOUTH CENTRAL TX BY THE END OF THE PERIOD. SATELLITE IMAGERY AND SURFACE DATA ALSO SUGGEST A CONVECTIVE BOUNDARY FROM CENTRAL AR INTO EAST CENTRAL OK WHICH MAY ENHANCE THUNDERSTORM ORGANIZATION AND INTENSITY THIS AFTERNOON AND EVENING. ...OK/AR/NRN TX/NRN LA... STRONG/SEVERE STORMS ARE CURRENTLY DEVELOPING OVER ERN OK AND EXTREME N CENTRAL TX AHEAD OF A SQUALL LINE ALONG THE DRY LINE FROM CENTRAL OK INTO THE WRN PARTS OF CENTRAL TX. VISIBLE SATELLITE IMAGERY SHOWS AREAS OF DIMINISHING CLOUDS OVER CENTRAL TX AND SERN OK AHEAD OF THE DRY LINE. THIS WILL PERMIT STRONGER DIURNAL HEATING WHICH WILL CONTRIBUTE TO FURTHER AIR MASS DESTABILIZATION DURING THE AFTERNOON. STEEP MID LEVEL LAPSE RATES OF 7.5-8.5 C/KM NOTED ON THE 12Z SOUNDINGS FROM MUCH OF TX WILL SPREAD ENEWD AHEAD OF THE UPPER TROUGH...WITH AXIS OF MOST UNSTABLE AIR MASS /CAPE OF 2500-3500 J/KG/ EXTENDING FROM N CENTRAL TX INTO SERN OK AND SWRN AR. COUPLING OF LOW LEVEL JET OF 45-55 KT FROM NERN TX INTO ERN OK/WRN AR WITH 75-80 KT MID LEVEL JET STREAK LIFTING NEWD ACROSS SERN OK WILL CREATE VERY STRONG VERTICAL SHEAR PROFILES WITH SFC-6 KM SHEAR GREATER THAN 30 M/S AND HELICITY VALUES OF 250-500 M2/S2. THIS INDICATES CONTINUED POTENTIAL FOR SUPERCELL DEVELOPMENT...AND SUFFICIENT MID LEVEL STORM-RELATIVE FLOW OF 20-30 KT SUGGESTS CONDITIONS WILL BECOME INCREASINGLY FAVORABLE FOR TORNADO DEVELOPMENT WITH PERSISTENT SUPERCELLS...INCLUDING THE POSSIBILITY OF A FEW INTENSE TORNADOES. AMPLE DRY AIR ALOFT ABOVE THE MOIST BOUNDARY LAYER WILL ENHANCE THE DOWNDRAFT POTENTIAL WITH THREAT OF DAMAGING WIND GUSTS...AND LARGE INSTABILITY WILL AID IN FORMATION OF LARGE HAIL. SEVERE STORMS ARE EXPECTED TO CONTINUE DEVELOPING AND SPREADING EWD/ENEWD FROM NRN TX/ERN OK INTO PARTS OF AR AND NRN LA INTO TONIGHT. ...CENTRAL PLAINS INTO THE MID MS VALLEY... UNSTABLE AIR MASS EXTENDS NWD INTO MUCH OF KS/NEB/IA/MO WHERE SURFACE DEW POINTS ARE IN THE 55-60 RANGE. DRY LINE IS MOVING NEWD ACROSS WRN/CENTRAL KS WHERE CLEAR SKIES WILL ALLOW STRONG HEATING THIS AFTERNOON. LOW LEVEL CONVERGENCE IS EXPECTED TO INCREASE NEAR THE SURFACE LOW AND DRY LINE WHICH SHOULD SUPPORT ADDITIONAL CONVECTIVE DEVELOPMENT THIS AFTERNOON AND EVENING. DYNAMIC FORCING ALOFT ASSOCIATED WITH LEFT EXIT REGION OF THE UPPER LEVEL JET STREAK WILL ENHANCE LARGE SCALE ASCENT. A FEW SEVERE STORMS ARE LIKELY TO SPREAD ACROSS PARTS OF KS AND INTO NEB THIS AFTERNOON AND EVENING...CONTINUING INTO MO AND WRN IA LATE THIS AFTERNOON AND EVENING. AS THE LOW LEVEL JET LIFTS TOWARD THE MID MS VALLEY LATER TONIGHT STRONG/SEVERE STORMS MAY PERSIST THROUGH THE OVERNIGHT HOURS. PRIMARY THREAT IS EXPECTED TO BE LARGE HAIL AND OCCASIONAL STRONG WIND GUSTS...BUT ISOLATED TORNADOES ARE ALSO POSSIBLE OVER PARTS OF KS AND NEB INTO THE EVENING HOURS. A PUBLIC SEVERE WEATHER OUTLOOK WILL BE ISSUED BY 1730Z. ..WEISS/MCCARTHY.. 05/04/99 ACUS1 KMKC 041939 SWODY1 MKC AC 041939 CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O. VALID 042000Z - 051200Z REF WW NUMBER 208 VALID TIL 2000Z. REF WW NUMBER 209 VALID TIL 0000Z. REF WW NUMBER 210 VALID TIL 0200Z. THERE IS A HIGH RISK OF SVR TSTMS THROUGH TONIGHT ACROSS A SMALL PART OF SOUTH CENTRAL MO...MUCH OF AR...PARTS OF NERN TX INTO NWRN LA. THE HIGH RISK IS RIGHT OF A LINE FROM 35 SSE SHV 20 SSE TYR 45 ESE DAL 40 WSW PRX 40 ENE DUA 35 ENE MLC 15 S UMN 10 NNW UNO 20 N ARG 60 WSW MEM 35 W GLH 25 WSW MLU 55 NW ESF 35 SSE SHV. SURROUNDING THE HIGH RISK...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF SRN MO SWD INTO NERN TX AND NRN LA AS WELL AS A SMALL PART OF WRN TN AND NWRN MS. THE MDT RISK AREA IS TO THE RIGHT OF A LINE FROM 45 E LFK 40 NNE CLL 10 ESE ACT 10 SSE DAL 15 ENE DUA 25 NNE MLC 45 SW JLN 50 SSW SZL 15 ENE JEF BLV 20 W PAH 15 NW UOX 35 SW GWO 30 WNW HEZ 15 SW ESF 45 E LFK. THERE IS ALSO A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 25 NW LCH 30 S AUS 30 NW AUS 45 S SEP 20 ESE FTW 25 WSW MLC 20 NE TUL 30 SW ICT 45 ENE DDC 60 WSW HLC 20 ESE MHN 40 ESE Y26 JMS 50 SSE FAR RWF 20 WNW ALO 10 E CMI 30 WSW BNA 20 NNW BHM 25 NE LUL 30 NNE LFT 25 NW LCH. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 55 NNW ELO 15 ESE RHI 25 NNW FWA 40 ESE LUK 25 NNE TYS 15 ENE LGC 20 SE PNS ...CONT... 40 ENE CRP 10 SW LRD ...CONT... 30 SSE DRT MWL 35 ENE OKC 20 SSW END 35 SSE GAG 40 N AMA 30 NW CAO 30 SSE PUB 35 WNW LIC 40 E CYS 30 SSE CDR 45 SSE PHP 20 WNW PIR 35 SSE BIS 50 NNE MOT. ...SEVERE THUNDERSTORM FORECAST DISCUSSION... ANOTHER DAY OF DANGEROUS STORMS CONTINUE TO DEVELOP AND INTENSIFY ACROSS PARTS OF THE ARKLATEX INTO CENTRAL AR. LATEST MESOSCALE ANALYSIS AT 18Z SHOWS SURFACE DRYLINE FROM CENTRAL KS SEWD/SWD THROUGH CENTRAL OK AND NORTH CENTRAL TX SWWD ACROSS THE MID RIO GRANDE VALLEY. SQUALL LINE OF SEVERE STORMS EXTENDS AHEAD OF THE DRYLINE FROM SERN KS INTO THE DFW METROPLEX...WITH SEVERAL SUPERCELL STORMS OCCURRING OVER WEST CENTRAL AR SWWD INTO NERN TX. AIR MASS AHEAD OF THE DRYLINE IS VERY UNSTABLE WITH BEST CAPE VALUES RANGING FROM 3500 TO 5000 J/KG FROM THE ARKLATEX AREA INTO PARTS OF CENTRAL TX. THIS AIR MASS EXISTS WITHIN ENVIRONMENT WITH STRONG DEEP LAYER SHEAR WITH 45-55 KT LOW LEVEL JET EXTENDING NWD FROM SOUTH CENTRAL LA INTO ERN MO UNDERNEATH EXIT REGION OF MID LEVEL 80-90 KT JET STREAK ACROSS WEST CENTRAL TX INTO NERN OK AND SWRN MO. RELATIVE HELICITY VALUES ARE RANGING FROM 400-500 M2/S2 ENHANCING ENVIRONMENT FOR SUPERCELL STORMS AND TORNADOES. SURFACE LOW OVER NORTH CENTRAL KS IS EXPECTED TO MOVE LITTLE THE REMAINDER OF THE PERIOD AS MID/UPPER LEVEL LOW SLOWLY CLOSES UP OVER THE NEB/KS BORDER. COLD FRONTAL BOUNDARY OVER THE OK/TX PANHANDLE WILL MOVE EWD INTO SERN KS/ERN OK THROUGH TONIGHT PUSHING SURFACE DRYLINE INTO CENTRAL/ERN AR BY THE END OF THE PERIOD. SEVERE STORMS WITH ISOLATED TORNADOES ARE EXPECTED TO CONTINUE THROUGH TONIGHT ACROSS PARTS OF ERN AR INTO PARTS OF NORTHERN LA. ..MCCARTHY.. 05/04/99 EXPERIMENTAL PROBABILITY GRAPHICS ARE UPDATED FOR THE DAY 1 CONVECTIVE OUTLOOKS AT 1300 AND 2000 UTC AND CAN BE FOUND ON THE SPC WEB PAGE AT: WWW.SPC.NOAA.GOV/PRODUCTS/ ACUS1 KMKC 041939 SWODY1 MKC AC 041939 CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O. VALID 042000Z - 051200Z REF WW NUMBER 208 VALID TIL 2000Z. REF WW NUMBER 209 VALID TIL 0000Z. REF WW NUMBER 210 VALID TIL 0200Z. THERE IS A HIGH RISK OF SVR TSTMS THROUGH TONIGHT ACROSS A SMALL PART OF SOUTH CENTRAL MO...MUCH OF AR...PARTS OF NERN TX INTO NWRN LA. THE HIGH RISK IS RIGHT OF A LINE FROM 35 SSE SHV 20 SSE TYR 45 ESE DAL 40 WSW PRX 40 ENE DUA 35 ENE MLC 15 S UMN 10 NNW UNO 20 N ARG 60 WSW MEM 35 W GLH 25 WSW MLU 55 NW ESF 35 SSE SHV. SURROUNDING THE HIGH RISK...THERE IS A MDT RISK OF SVR TSTMS ACROSS MUCH OF SRN MO SWD INTO NERN TX AND NRN LA AS WELL AS A SMALL PART OF WRN TN AND NWRN MS. THE MDT RISK AREA IS TO THE RIGHT OF A LINE FROM 45 E LFK 40 NNE CLL 10 ESE ACT 10 SSE DAL 15 ENE DUA 25 NNE MLC 45 SW JLN 50 SSW SZL 15 ENE JEF BLV 20 W PAH 15 NW UOX 35 SW GWO 30 WNW HEZ 15 SW ESF 45 E LFK. THERE IS ALSO A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 25 NW LCH 30 S AUS 30 NW AUS 45 S SEP 20 ESE FTW 25 WSW MLC 20 NE TUL 30 SW ICT 45 ENE DDC 60 WSW HLC 20 ESE MHN 40 ESE Y26 JMS 50 SSE FAR RWF 20 WNW ALO 10 E CMI 30 WSW BNA 20 NNW BHM 25 NE LUL 30 NNE LFT 25 NW LCH. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 55 NNW ELO 15 ESE RHI 25 NNW FWA 40 ESE LUK 25 NNE TYS 15 ENE LGC 20 SE PNS ...CONT... 40 ENE CRP 10 SW LRD ...CONT... 30 SSE DRT MWL 35 ENE OKC 20 SSW END 35 SSE GAG 40 N AMA 30 NW CAO 30 SSE PUB 35 WNW LIC 40 E CYS 30 SSE CDR 45 SSE PHP 20 WNW PIR 35 SSE BIS 50 NNE MOT. ...SEVERE THUNDERSTORM FORECAST DISCUSSION... ANOTHER DAY OF DANGEROUS STORMS CONTINUE TO DEVELOP AND INTENSIFY ACROSS PARTS OF THE ARKLATEX INTO CENTRAL AR. LATEST MESOSCALE ANALYSIS AT 18Z SHOWS SURFACE DRYLINE FROM CENTRAL KS SEWD/SWD THROUGH CENTRAL OK AND NORTH CENTRAL TX SWWD ACROSS THE MID RIO GRANDE VALLEY. SQUALL LINE OF SEVERE STORMS EXTENDS AHEAD OF THE DRYLINE FROM SERN KS INTO THE DFW METROPLEX...WITH SEVERAL SUPERCELL STORMS OCCURRING OVER WEST CENTRAL AR SWWD INTO NERN TX. AIR MASS AHEAD OF THE DRYLINE IS VERY UNSTABLE WITH BEST CAPE VALUES RANGING FROM 3500 TO 5000 J/KG FROM THE ARKLATEX AREA INTO PARTS OF CENTRAL TX. THIS AIR MASS EXISTS WITHIN ENVIRONMENT WITH STRONG DEEP LAYER SHEAR WITH 45-55 KT LOW LEVEL JET EXTENDING NWD FROM SOUTH CENTRAL LA INTO ERN MO UNDERNEATH EXIT REGION OF MID LEVEL 80-90 KT JET STREAK ACROSS WEST CENTRAL TX INTO NERN OK AND SWRN MO. RELATIVE HELICITY VALUES ARE RANGING FROM 400-500 M2/S2 ENHANCING ENVIRONMENT FOR SUPERCELL STORMS AND TORNADOES. SURFACE LOW OVER NORTH CENTRAL KS IS EXPECTED TO MOVE LITTLE THE REMAINDER OF THE PERIOD AS MID/UPPER LEVEL LOW SLOWLY CLOSES UP OVER THE NEB/KS BORDER. COLD FRONTAL BOUNDARY OVER THE OK/TX PANHANDLE WILL MOVE EWD INTO SERN KS/ERN OK THROUGH TONIGHT PUSHING SURFACE DRYLINE INTO CENTRAL/ERN AR BY THE END OF THE PERIOD. SEVERE STORMS WITH ISOLATED TORNADOES ARE EXPECTED TO CONTINUE THROUGH TONIGHT ACROSS PARTS OF ERN AR INTO PARTS OF NORTHERN LA. ..MCCARTHY.. 05/04/99 EXPERIMENTAL PROBABILITY GRAPHICS ARE UPDATED FOR THE DAY 1 CONVECTIVE OUTLOOKS AT 1300 AND 2000 UTC AND CAN BE FOUND ON THE SPC WEB PAGE AT: WWW.SPC.NOAA.GOV/PRODUCTS/ ACUS1 KMKC 050101 SWODY1 MKC AC 050101 CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O. VALID 050100Z - 051200Z THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 40 SW HEZ LFK 55 SW TYR 35 W TYR 40 NW HOT 35 ENE HRO 30 E SGF 30 NE JLN 30 SSW EMP 30 NE SLN 35 NNE CNK 25 ESE OLU 45 SSW FOD MLI 10 E CMI 30 WSW BWG 20 NNW BHM MEI 40 SW HEZ. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 45 SE HUM 25 WNW MSY 35 N LFT 20 SW LFK 60 NNE CLL 60 SSE DAL 25 E PGO 25 ESE MKO 40 SSW END 45 NNE GAG 30 SE MHN 45 SW BIS 50 NNE MOT ...CONT... 55 NNW ELO AUW 25 NNW FWA 40 ESE LUK 25 NNE TYS 35 E VLD 30 SSE CTY. ...SEVERE THUNDERSTORM FORECAST DISCUSSION... WIDESPREAD CONVECTION CONTINUES TO INCREASE WITHIN WEAKLY CAPPED AIR MASS ACROSS AR/ERN MO...WHICH HAS DIMINISHED LAPSE RATES AND LIMITED FURTHER INSTABILITY ACROSS THIS REGION. WIND FIELDS REMAIN STRONG HOWEVER AND SHOULD MAINTAIN SOME POTENTIAL FOR A FEW SEVERE THUNDERSTORMS...FROM NRN LA INTO THE MID MS RIVER VALLEY. VERY LOW LCL HEIGHTS WITHIN VERY MOIST BOUNDARY LAYER /IE. SATURATED TO NEAR H7 AT SHV...JAN...SIL THIS EVENING/ AND STRONG LOW LEVEL SHEAR WILL ALSO MAINTAIN A THREAT OF ISOLATED TORNADOS. MAIN UPPER TROUGH OVER THE CENTRAL PLAINS APPEARS TO BE LIFTING NEWD AT THIS TIME...AND SHOULD SHIFT STRONGEST UVV/S AND 50-60 KT LLJ EWD INTO THE MS RIVER AND LOWER OH RIVER VALLEYS THROUGH THE NIGHT. THIS MAY SUPPORT A MORE LINEAR ORGANIZATION TO THE CONVECTION LATER TONIGHT INTO THIS REGION...WITH PERSISTENT DAMAGING WINDS THREAT. IN ADDITION...LAPSE RATES REMAIN STEEP UNDER COLD POOL OVER THE SRN PLAINS WHICH WILL CONTINUE ADVECTING NEWD INTO MO AND POSSIBLY IA. THIS COULD MAINTAIN A SLIGHT RISK OF HAIL ACROSS THESE AREAS THROUGH THE EVENING. ATTENDANT ISOLATED TORNADO THREAT OVER NERN KS SHOULD DIMINISH OVER THE NEXT HOUR OR SO AS LOW LEVELS STABILIZE AFTER SUNSET. ..EVANS.. 05/05/99 CONVECT>