ZCZC SPCSWODY1 ALL ACUS01 KWNS 121311 SPC AC 121309 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 121300Z - 131200Z THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM 30 WSW ADM 40 NW OKC 30 NNE P28 15 W TOP 50 NW COU 25 WNW STL 55 WNW CGI 40 SW UNO 10 SSW FSM 10 NNW DUA 30 WSW ADM. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 25 SW PSX 40 NW HOU 15 W LFK 25 SSE GGG 35 NNW GGG 40 NNE ACT 20 W SEP 25 SSE LTS 25 E GAG 45 N P28 25 NNW SLN 10 ENE FNB 45 SE DTW 20 NNW YNG 30 S HLG 15 ENE HTS 45 SSE PAH 45 WSW MEM 30 ESE PBF 40 SW GLH 50 NW JAN 50 NW MEI 15 W 0A8 30 S ATL 40 WSW AGS 30 SSW CHS. ...SYNOPSIS... PROGRESSIVE UPPER LEVEL FLOW OVER THE NRN HALF OF THE U.S. WILL BECOME MORE AMPLIFIED TODAY AS A PACIFIC TROUGH APPROACHING THE WEST COAST TOWARD THE END OF THE PERIOD INDUCES HEIGHT RISES DOWNSTREAM OVER THE ROCKIES INTO THE PLAINS. AS THIS OCCURS...A WEAK SHORT WAVE TROUGH...CURRENTLY MOVING THROUGH WRN MT/NWRN WY PER EARLY MORNING WV IMAGERY...WILL AMPLIFY AS IT TRACKS ESEWD TO WRN MN AND NERN KS BY 00Z AND THEN TO THE OH/MID MS VALLEYS OVERNIGHT. SOMEWHAT WEAKER WLY FLOW WILL CONTINUE WITHIN THE SRN STREAM FROM NRN MEXICO TO THE GULF COAST STATES. ...ERN KS/MO/NWRN AR/CENTRAL-ERN OK... EARLY MORNING SURFACE ANALYSIS SHOWS A WEAK SURFACE LOW OVER SERN CO/OK PANHANDLE...WHILE A COLD FRONT WAS MOVING SWD THROUGH CENTRAL NEB AND SWRN TO CENTRAL IA. SLY LOW-LEVEL FLOW OVER THE SRN PLAINS WAS CONTINUING TO ADVECT MOISTURE NWD THIS MORNING WITH MID-UPPER 50 SURFACE DEWPOINTS AS FAR NORTH AS CENTRAL OK AND 60 SURFACE DEWPOINTS INTO S CENTRAL/SWRN OK. 06Z ETA IS VERIFYING WELL WITH THIS NWD MOISTURE ADVECTION AND APPEARS REASONABLE FOR 60 F SURFACE DEWPOINTS TO REACH SE KS/SW MO BY LATE AFTERNOON. WITH AFTERNOON SURFACE TEMPERATURES EXPECTED IN THE LOWER-MID 70S OVER SERN KS/ SWRN MO/NERN OK AND STEEPENING MID-LEVEL LAPSE RATES WILL RESULT IN MLCAPE VALUES NEAR 2500 J/KG. THE SURFACE LOW INITIALLY OVER SERN CO/OK PANHANDLE WILL WEAKEN AS IT MOVES INTO WRN/SWRN OK AND WEAKEN THIS AFTERNOON AS A DRY LINE TRACKS EWD FROM WRN TX INTO WRN OK/CENTRAL TX. MEANWHILE...A SECOND LOW IS PROGGED TO DEVELOP OVER SRN KS /NEAR ICT/ THIS AFTERNOON AS THE COLD FRONT MOVES SWD INTO KS/MO. CONVECTIVE INITIATION REMAINS MOST LIKELY OVER E/SE KS INTO W CENTRAL MO... BETWEEN 21-00Z...ALONG THE COLD FRONT /NE OF THE SURFACE LOW/ AND AS THE SRN EXTENT OF A MID-LEVEL TROUGH MOVES INTO KS. CONVECTIVE INITIATION IS ALSO POSSIBLE FARTHER SOUTH INTO SRN KS ALONG THE COLD FRONT AND INTO CENTRAL OK ALONG THE DRY LINE. TSTMS WILL BE LESS LIKELY OVER NRN TX WHERE FORCING FOR ASCENT WILL BE WEAK ALONG THE DRY LINE AND POINT FORECAST SOUNDINGS SHOW THIS AREA REMAINING CAPPED THROUGH THE AFTERNOON INTO THE EVENING. ALTHOUGH STRONGER MID-LEVEL FLOW IS EXPECTED TO REMAIN NORTH OF THE SLIGHT RISK AREA...30-40 KT WLY MID-LEVEL WINDS COMBINED WITH A DEVELOPING 30-35 KT SSWLY LLJ OVER ERN OK INTO SWRN MO/SERN KS WILL RESULT IN FAVORABLE LOW AND DEEP LAYER SHEAR FOR ORGANIZED STORMS WITH SUPERCELLS. MEANWHILE...WEAKER ASCENT SWD ALONG THE DRY LINE IN CENTRAL/SRN OK WITH 0-6 KM SHEAR VECTORS PERPENDICULAR TO THE DRY LINE WILL FAVOR THE POTENTIAL FOR DISCRETE SUPERCELLS...THOUGH SOME CONVECTIVE INHIBITION SHOULD KEEP THE COVERAGE ISOLATED. EXPECT STORMS TO DEVELOP INTO A BAND FROM CENTRAL/SWRN MO INTO SERN KS/NERN OK AND NWRN AR THIS EVENING...WITH ACTIVITY SPREADING E AND S OVERNIGHT. LARGE HAIL/DAMAGING WINDS WILL BE THE PRIMARY THREATS GIVEN THE COMBINATION OF INSTABILITY...STEEP LAPSE RATES WITH COOL MID-LEVEL TEMPERATURES AND SUFFICIENT DEEP LAYER SHEAR. HOWEVER... ISOLATED TORNADOES WILL BE POSSIBLE PRIMARILY OVER SERN KS/NERN OK/ SWRN MO/NWRN AR...WHERE SURFACE-1 KM SHEAR VALUES BECOME FAVORABLE FOR TORNADOES WITH THE STRENGTHENING LLJ AND TO THE EAST OF THE SURFACE LOW...WHERE SURFACE WINDS MAY BE LOCALLY BACKED. ..PETERS.. 03/12/03 NNNN |