SWODY1
SPC AC 061251
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CDT THU SEP 06 2007
VALID 061300Z - 071200Z
..THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
FROM THE CENTRAL PLAINS TO THE UPPER MS VALLEY...
..PLAINS AREA THIS AFTERNOON INTO TONIGHT...
THE MID LEVEL SHORTWAVE TROUGH OVER UT/ERN ID/WRN WY THIS MORNING
WILL ACCELERATE EWD TO WRN NEB BY THIS EVENING AND THE MIDDLE-UPPER
MS VALLEY TONIGHT...WHILE PHASING WITH AN AMPLIFYING NRN STREAM. A
STALLED NE-SW ORIENTED FRONT FROM NW NEB TO NW MN WILL PROVIDE A
FOCUS FOR CYCLOGENESIS LATER TODAY INTO TONIGHT ACROSS MN/NW WI...IN
ADVANCE OF THE EJECTING MID LEVEL WAVE. LEE CYCLOGENESIS WILL OCCUR
INVOF WRN KS IN CONJUNCTION WITH THE SRN FRINGE OF THE STRONGER MID
LEVEL WLY FLOW...BEFORE THE SURFACE COLD FRONT SURGES SEWD OVERNIGHT
IN THE WAKE OF THE DEEPENING SURFACE LOW AND MID LEVEL WAVE. THE
SURFACE BAROCLINIC ZONE WILL BE THE PRIMARY FOCUS FOR SEVERE STORM
DEVELOPMENT THIS AFTERNOON INTO TONIGHT.
BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S TO LOWER 70S ARE ALREADY
PRESENT IN THE WARM SECTOR FROM ERN KS NWD TO ERN SD/WRN MN.
DAYTIME HEATING OF THIS MOIST BOUNDARY LAYER WILL CONTRIBUTE TO THE
DEVELOPMENT OF MODERATE INSTABILITY E OF THE LEE CYCLONE AND ALONG
THE FRONT THIS AFTERNOON...WITH MLCAPE VALUES RANGING FROM 2000-2500
J/KG ACROSS CENTRAL KS/NEB TO 1500 J/KG ACROSS WRN MN.
THE INITIAL CONVECTION MAY FORM OVER THE HIGH PLAINS BY MID
AFTERNOON IN CONJUNCTION WITH THE EJECTING MID LEVEL TROUGH...W OF
THE PRIMARY SURFACE FRONT IN NEB. ADDITIONAL STORMS SHOULD ALSO
FORM ALONG THE FRONT BY LATE AFTERNOON.
THE POSSIBILITY OF MULTIPLE STORM INTERACTIONS AND THE STRONGER
MID-UPPER FLOW LAGGING THE WARM SECTOR BOTH SUGGEST THAT CONVECTION
MAY TRANSITION TO A LINEAR MODE RATHER QUICKLY. IF DISCRETE
CONVECTION CAN FORM ALONG THE FRONT BY LATE AFTERNOON...DEEP LAYER
VERTICAL SHEAR WILL BE AT LEAST MARGINALLY FAVORABLE FOR SUPERCELLS.
STRONGER LOW-LEVEL FLOW IS FORECAST TO DEVELOP THIS EVENING ACROSS
NE KS/SE NEB WITH THE STRENGTHENING LLJ...BUT IT IS NOT CLEAR THAT
CONVECTION WILL BE ABLE TO FORM E OF THE FRONT. LARGE HAIL AND
DAMAGING WINDS WILL BE THE MOST COMMON SEVERE STORM THREATS THIS
AFTERNOON/EVENING...WITH PRIMARILY A DAMAGING WIND THREAT OVERNIGHT.
A COUPLE OF TORNADOES MAY ALSO OCCUR WITH EITHER THE INITIAL
DEVELOPMENT ON THE FRONT... OR ANY DISCRETE STORMS THAT HAPPEN TO
FORM LATER IN THE EVENING AS LOW-LEVEL SHEAR INCREASES.
..SRN MO INTO WRN IL TODAY...
A MID LEVEL LOW OVER WRN MO THIS MORNING WILL EVOLVE INTO AN OPEN
WAVE AND ACCELERATE NEWD OVER IL/INDIANA BY TONIGHT. THROUGH
TODAY...A BELT OF ROUGHLY 30 KT LOW-MID LEVEL FLOW WILL BE
MAINTAINED ON THE SERN PERIPHERY OF THE MID LEVEL TROUGH. MOIST
PROFILES AND WEAK INSTABILITY COULD SUPPORT A FEW ROTATING STORMS
AND AN ATTENDANT THREAT FOR A BRIEF/WEAK TORNADO AND ISOLATED STRONG
GUSTS.
..SE AZ/SRN NM/W TX TODAY...
THE REMNANTS OF TC HENRIETTE WILL SPREAD NEWD FROM NW MEXICO ACROSS
SRN NM. WIDESPREAD CLOUDS/RAINFALL WILL TEND TO LIMIT LAPSE
RATES/INSTABILITY...WITH THE STRONGER INSTABILITY EXPECTED ON THE
FRINGES OF THE WEAKENING WARM CORE SYSTEM ACROSS AZ AND W TX. GIVEN
THE WEAK INSTABILITY AND WEAKENING WIND FIELDS WITH TIME...THE
SEVERE STORM THREAT APPEARS TO BE NEGLIGIBLE.
.THOMPSON/GRAMS.. 09/06/2007
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