ACUS1 KMKC 041057 SWODY1 MKC AC 041057 CONVECTIVE OUTLOOK...REF AFOS NMCGPH94O. VALID 041200Z - 051200Z THERE IS A MDT RISK OF SVR TSTMS OVER CENTRAL/ERN KS...N-CENTRAL/ NERN OK...PART OF SERN NEB...PARTS OF W-CENTRAL/NWRN MO...AND A SMALL PART OF SWRN IA...TO THE RIGHT OF A LINE FROM 50 SSW SZL 15 NNW MKO 25 ESE END 10 NE RSL 25 ESE HSI 30 ESE OMA 35 NE P35 50 SSW SZL. THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 35 SE FSM 35 E DAL 45 SSW SPS 50 SW END 20 E DDC 20 W MCK 40 SSW ANW 25 ESE FSD 30 S RST 35 NNE MLI 25 S SPI 50 NW P02 35 SE FSM. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 ESE P07 40 SSE BGS 45 N ABI 30 NW CSM 25 NNW LBL 35 SSW LHX 20 E FMN 35 SSE U17 35 ENE 4LW 25 ESE PDX 35 E BLI ...CONT... 50 NE HVR 55 NE HVR 35 WNW RAP 35 N PHP 25 SE Y26 40 SSW DVL 15 W TVF 45 ENE BJI 10 NW IWD 10 NW MBL 15 NW JXN 10 W FDY 15 WNW CRW 30 SSE PSK 40 NE RDU 35 ENE ORF. ...SEVERE THUNDERSTORM FORECAST DISCUSSION... --- SYNOPSIS --- HIGH-AMPLITUDE UPPER LEVEL TROUGH IS EVIDENT ON MOISTURE CHANNEL IMAGERY FROM NEAR BC/ALTA BORDER SSEWD INTO NWRN NM. SHORTWAVE TROUGH IN ITS BASE OVER SWRN CO/NWRN NM IS BECOMING MORE NEGATIVELY TILTED...WITH VERY STRONG DIFLUENCE DOWNSTREAM ACROSS CENTRAL/SRN HIGH PLAINS. TROUGH IS FORECAST TO EJECT ENEWD ACROSS CENTRAL PLAINS TO IA BY END OF PERIOD...AS A CYCLONE DEVELOPS ALOFT OVER SD. SURFACE CYCLONE IS STRENGTHENING OVER SERN CO...WHILE BAROCLINIC GRADIENT IS TIGHTENING N OF WARM FRONT ANALYZED ESEWD ACROSS EXTREME SRN KS. WARM FRONT IS FORECAST TO MOVE NEWD ACROSS MUCH OF KS TODAY AND MOST OF MO TONIGHT...WHILE COLD FRONT NOW TRAILING CYCLONE IN SERN CO SWEEPS SEWD OVER WRN KS AND WRN OK. COMBINATION OF VERTICAL MIXING AND DRY ADVECTION OVER HIGH PLAINS WILL RESULT IN EWD MOVEMENT OF DRYLINE FROM CURRENT TX PANHANDLE/SERN CO POSITION...TO ROUGHLY SJT/END/HUT LINE BY MID/LATE AFTERNOON. ... 04/12Z-05/03Z ... --- CENTRAL PLAINS EARLY --- STRONG ELEVATED WAA/DESTABILIZATION REGIME IS UNDERWAY WELL N OF SURFACE WARM FRONT OVER NRN KS AND NEB...IN WHICH SEVERAL CLUSTERS OF THUNDERSTORMS ARE EXPANDING/INTENSIFYING. FORECAST SOUNDINGS SHOW ELEVATED MUCAPE AROUND 2000 J/KG AT 04/12Z...AND SLIGHTLY WEAKER LLJ THAN CURRENTLY OBSERVED IN AREA VWP/PROFILER DATA. EXPECT MORNING PREFRONTAL ACTIVITY NRN KS/NEB WILL PRODUCE LARGE HAIL...WITH ISOLATED SIGNIFICANT/DAMAGING HAIL POSSIBLE GIVEN MAGNITUDE OF INSTABILITY OVER FRONTAL LAYER. --- AFTERNOON/EVENING...CENTRAL/SRN PLAINS --- REGIONAL OUTBREAK OF SEVERE THUNDERSTORMS IS EXPECTED OVER MUCH OF MDT RISK AREA...INCLUDING SEVERAL SUPERCELLS WITH THE POTENTIAL FOR SIGNIFICANT TORNADOES...DESTRUCTIVE HAIL AND SEVERE GUSTS. SUPERCELLS ARE EXPECTED TO DEVELOP E OF SURFACE CYCLONE INVOF WARM FRONT...AND NEAR DRYLINE OVER PORTIONS CENTRAL KS AND NRN OK...THIS AFTERNOON...AND QUICKLY BECOME SEVERE. ATTM...TORNADO PROBABILITIES APPEAR GREATEST OVER CENTRAL KS WITHIN 3-4 HOURS AFTER CONVECTIVE INITIATION...BUT ARE LARGE ENOUGH ELSEWHERE FROM NEAR KS/NEB BORDER TO N-CENTRAL OK TO WARRANT ENHANCED RISK. CAPPING WILL INCREASE SWD ALONG DRYLINE ACROSS WRN/CENTRAL OK INTO NWRN TX...BUT ANY STORMS THAT DEVELOP IN THOSE AREAS SHOULD ROTATE AND PRODUCE SIGNIFICANT SEVERE ALSO. LATEST SURFACE ANALYSES SHOW A PRONOUNCED WEDGE OF RICH MOISTURE WITH DEWPOINTS IN UPPER 60S TO LOW 70S F SPREADING RAPIDLY NNWWD INTO S-CENTRAL/SWRN KS...IN RESPONSE TO STRONG PRESSURE FALLS FROM NWRN OK TO SWRN NEB. 70S DEW POINTS WILL BE QUITE COMMON ALONG AND S OF WARM FRONT THIS AFTERNOON...COMBINING WITH INSOLATION TO YIELD MLCAPE 3000-4000 J/KG. MODERATE-STRONG VERTICAL SHEAR PROFILES ARE EXPECTED THIS AFTERNOON FROM INVOF KS/NEB BORDER SWD ACROSS WARM FRONT...AND IN WARM SECTOR AS FAR S AS N-CENTRAL OK. SHEAR FAVORABLE FOR TORNADIC SUPERCELLS MAY EXTEND FARTHER S INTO SLGT RISK ZONE OVER CENTRAL/SRN OK. STORM-RELATIVE HELICITIES 250-500 J/KG FORECAST OVER THIS CORRIDOR...WITH BRN SHEAR IN 80-110 J/KG RANGE AND STORM-RELATIVE FLOW AOA 20 KT THROUGH MOST OF THE LOWER- MIDDLE TROPOSPHERE. TRANSITION TO DAMAGING WIND EVENT IS LIKELY NEAR END OF FIRST PERIOD ESPECIALLY FROM CENTRAL/ERN KS NEWD...AS CONVECTIVE COVERAGE BECOMES MORE DENSE AND A SEVERE MCS DEVELOPS. ... 05/03Z-05/12Z ... --- SRN PLAINS THRU MO/IA --- PRIND STRONG LOW LEVEL CONVERGENCE AND ABUNDANT MOISTURE WILL SUPPORT A BAND OF STRONG AND SEVERE THUNDERSTORMS EARLY IN PERIOD...MOVING ENEWD ACROSS LOWER MO VALLEY AREA OF SERN NEB/WRN IA/NERN KS/NWRN MO. THIS BAND SHOULD BUILD SWWD INTO MORE UNSTABLE LOW LEVEL AIR MASS AS FAR AS CENTRAL/ERN OK WITH TIME...FILLING IN AS A LONG ARC OF INTENSE CONVECTION AS IT MERGES WITH ANY REMAINING THUNDERSTORMS OF DRYLINE ORIGIN OVER OK. AS THIS PROCESS OCCURS...MAIN SEVERE THREAT WILL BECOME DAMAGING WIND. CAPPING WILL REMAIN STRONG OVER SRN OK AND NRN TX AND MID LEVEL FLOW WILL WEAKEN SWD. OUTLOOK OVER THIS AREA IS SUBSTANTIALLY MORE CONDITIONAL...BUT SRN PORTION OF KS/OK COMPLEX MAY TRAIL INTO THIS AREA...WITH THREAT FOR LARGE HAIL AND DAMAGING WIND. ... A PUBLIC SEVERE WEATHER OUTLOOK IS BEING ISSUED ON THIS POTENTIALLY DANGEROUS SITUATION ... ..EDWARDS.. 10/04/98