ZCZC SPCSWODY1 ALL ACUS01 KWNS 270558 SPC AC 270557 STORM PREDICTION CENTER...NWS/NCEP...NORMAN OK DAY 1 CONVECTIVE OUTLOOK...REF AWIPS GRAPHIC PGWE46 KWNS. VALID 271200Z - 281200Z THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM MIA 35 NNW MIA 30 SW VRB ORL DAB. THERE IS A SLGT RISK OF SVR TSTMS TO THE RIGHT OF A LINE FROM OKC BVO SZL IRK BRL PIA BMI LAF HUF PAH 15 NNE LIT TXK PRX ADM OKC. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 60 NNW GGW 55 WSW MLS 30 SSW DGW 35 ENE DEN 25 W LHX 30 ENE RTN 30 WSW RTN 45 N 4SL 20 NE U17 60 SW DPG 10 SSE OWY 45 WNW OWY 70 NNW BNO 55 WSW PDT 30 SSW 63S 45 NE 63S. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 15 S PNS 35 SSE SEM 20 WSW AND 35 WSW GSO 55 S RIC 30 NE ORF. GEN TSTMS ARE FCST TO THE RIGHT OF A LINE FROM 65 NW ERI 15 N CAK 30 SSW HTS 20 S BNA 25 N TUP 45 NNW GWO 15 SW ELD 35 NE GGG 15 SE FTW 15 SE SPS OKC 25 NNE BVO 30 SSE TOP OMA 35 NNE FOD 40 NNW OSH ANJ. MODELS INDICATE AMPLIFYING UPPER FLOW PATTERN FROM THE CENTRAL PACIFIC INTO THE CENTRAL U.S. DURING THIS FORECAST PERIOD. AS UPPER RIDGE BUILDS ACROSS THE EASTERN PACIFIC...LONG WAVE TROUGH IS PROGGED TO GRADUALLY EVOLVE DOWNSTREAM...ENCOMPASSING MUCH OF THE NATION FROM THE INTERMOUNTAIN WEST INTO THE MISSISSIPPI VALLEY. FARTHER DOWNSTREAM...MODELS SUGGEST SPLIT FLOW REGIME WILL PERSIST ...BUT SOUTHERN BRANCH CLOSED LOW/SHORT WAVE TROUGH IS PROGGED TO MIGRATE EAST NORTHEASTWARD OUT OF THE CENTRAL GULF OF MEXICO INTO THE SOUTHEAST STATES. ...FLORIDA... CLUSTER OF CONVECTION WITH LARGE RAIN SHIELD APPEARS LIKELY TO BE ONGOING AT 27/12Z...FROM PARTS OF THE NORTHEAST GULF OF MEXICO INTO NORTHERN FLORIDA...BENEATH STRONGLY DIFLUENT/DIVERGENT UPPER FLOW REGIME NORTH/NORTHEAST OF CLOSED LOW. SOUTH OF THIS ACTIVITY... CLOUDS/PRECIPITATION LIKELY TO OVERSPREAD MUCH OF THE FLORIDA PENINSULA DURING THE MORNING HOURS PROVIDES SOME UNCERTAINTY WITH REGARD TO EXTENT OF CONVECTIVE THREAT. HOWEVER...CONTINUED MOISTENING OF LOW-LEVELS WILL CONTRIBUTE TO DESTABILIZATION...AS WEAK SOUTHERLY LOW-LEVEL JET DEVELOPS WITH APPROACH OF UPPER TROUGH. AS SURFACE DEW POINTS CLIMB INTO THE UPPER 60S...ETA POINT FORECAST SOUNDINGS INDICATE CAPE EXCEEDING 1000 J/KG ALONG ATLANTIC COASTAL AREAS...WHERE LOW-LEVEL TROUGHING/CONVERGENCE WILL BECOME ENHANCED. INSTABILITY/LIFT IS EXPECTED TO SUPPORT INCREASING/INTENSIFYING THUNDERSTORM ACTIVITY BY/SHORTLY AFTER 27/18Z...WHEN VERTICAL SHEAR PROFILES WILL BECOME SUPPORTIVE OF SUPERCELLS. MODELS INDICATE MODERATELY STRONG FLOW WITH SUBSTANTIAL VEERING WITH HEIGHT IN LOWER/MID-LEVELS...BENEATH STRONG UPPER JET...SUPPORTIVE OF ISOLATED TORNADIC SUPERCELLS IN INCREASINGLY FAVORABLE THERMODYNAMIC ENVIRONMENT. MOST INTENSE ACTIVITY APPEARS LIKELY IN THE MELBOURNE/VERO BEACH AREAS...BEFORE SHIFTING OFFSHORE LATE THIS AFTERNOON. ...CENTRAL PLAINS... SIGNIFICANT RETURN FLOW OF MOISTURE DOES NOT APPEAR LIKELY TO OCCUR TO THE SOUTHERN PLAINS/MISSISSIPPI VALLEY DURING THIS FORECAST PERIOD...DUE TO GULF OF MEXICO SYSTEM. THIS PROVIDES CONSIDERABLE UNCERTAINTY WITH REGARD TO EXTENT OF SEVERE THREAT AS LEAD SHORT WAVE TROUGH/EXIT REGION OF INTENSE CYCLONIC HIGH-LEVEL JET SHIFTS ACROSS THE CENTRAL PLAINS/MIDDLE MISSISSIPPI VALLEY LATE THIS AFTERNOON AND TONIGHT. HOWEVER...WEAK TO MODERATE POTENTIAL INSTABILITY APPEARS LIKELY TO DEVELOP BY LATE AFTERNOON...WHERE STRONG HEATING/STEEP MID-LEVEL LAPSE RATES ARE LIKELY TO DEVELOP ALONG LOW-LEVEL THERMAL RIDGE AXIS FROM CENTRAL OKLAHOMA INTO WESTERN MISSOURI. MID-LEVEL CAP IS EXPECTED TO PROVE INHIBITIVE TO CONVECTIVE DEVELOPMENT...LIKELY UNTIL THE EARLY EVENING HOURS...WHEN STRONG FORCING FOR UPWARD VERTICAL MOTION NEAR COLD FRONT ZONE SUPPORTS CONVECTIVE INITIATION. BROKEN SQUALL LINE APPEARS POSSIBLE BY THE LATE EVENING HOURS...WITH LARGE HAIL ACCOMPANYING STRONGEST CELLS. SOME STRENGTHENING APPEARS POSSIBLE OVERNIGHT AS ACTIVITY SPREADS OUT OF EASTERN MISSOURI INTO ILLINOIS...WHEN/WHERE MODELS SUGGEST SOMEWHAT BETTER MOISTURE RETURN/SURFACE-BASED DESTABILIZATION IN WARM SECTOR SOUTHEAST OF DEEP SURFACE CYCLONE. ..KERR/JEWELL.. 03/27/03 NNNN |