SWODY1
SPC AC 070550
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1250 AM CDT FRI SEP 07 2007
VALID 071200Z - 081200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS ACROSS THE
MS VALLEY TO LOWER MI...
..SYNOPSIS...
MID/UPPER LEVEL TROUGH NOW CROSSING THE CNTRL PLAINS IS FORECAST TO
DEAMPLIFY AND BECOME INCREASINGLY ABSORBED INTO STRONG WLY FLOW
ACROSS SRN CANADA AS BELT OF RELATIVELY FAST FLOW PERSISTS ACROSS
THE NRN STATES. AS THIS IMPULSE ACCELERATES NEWD FROM THE UPPER MS
VALLEY TO THE GREAT LAKES THIS AFTERNOON...ASSOCIATED SURFACE
CYCLONE WILL INTENSIFY WHILE TRACKING TOWARD JAMES BAY. COLD FRONT
WITH THIS SYSTEM WILL MOVE QUICKLY EAST ACROSS WRN GREAT LAKES AND
UPPER MIDWEST AREAS THROUGH THE AFTERNOON. FARTHER SW...TRAILING
EXTENSION OF THE COLD FRONT...INTERSPERSED WITH CONVECTIVE
OUTFLOWS...WILL SETTLE SEWD ACROSS THE MIDDLE MS VALLEY...AND SWD
ACROSS SRN PLAINS BENEATH WEAKER FLOW AND FORCING ALOFT.
NEXT UPSTREAM LOW-AMPLITUDE IMPULSE EMBEDDED WITHIN FAST FLOW WILL
SPREAD ESEWD ACROSS THE NRN ROCKIES THROUGH THE AFTERNOON WITH
POCKET OF STRONG HEIGHT FALLS MOVING FROM MT TO THE WRN DAKOTAS
THROUGH THE END OF THE FORECAST PERIOD.
..SRN PLAINS ACROSS THE MS VALLEY TO LOWER MI...
AREAS OF CONVECTION...BOTH ALONG AND AHEAD OF THE DEEP-LAYER FRONTAL
ZONE...SHOULD BE ONGOING ACROSS PARTS OF KS/MO NEWD TO IL AND THE
GREAT LAKES EARLY TODAY. STRONGER LARGE SCALE FORCING ASSOCIATED
WITH THE SHORT WAVE TROUGH MOVING ACROSS THE NRN GREAT LAKES AREA
SHOULD SUSTAIN SUFFICIENT LIFT ALONG AND AHEAD OF THE ADVANCING COLD
FRONT FOR TSTMS TO CONTINUE EAST INTO LOWER MI AND PARTS OF IND/IL
INTO THE AFTERNOON. THIS PROCESS SHOULD UNFOLD COINCIDENT WITH A
MODEST INCREASE IN WARM SECTOR DESTABILIZATION ACROSS THESE AREAS SO
THAT STORM INTENSITY GRADUALLY INCREASES THROUGH THE AFTERNOON.
SHEAR AND LINEAR FORCING ALONG THE ADVANCING FRONTAL ZONE APPEAR
ADEQUATE FOR LINE SEGMENTS AND PERHAPS SOME EMBEDDED SUPERCELL
STRUCTURES TO EVOLVE WITH ATTENDANT THREATS OF HAIL AND DAMAGING
WINDS.
FARTHER SW...FROM IL SWWD ACROSS MO TO KS/OK...FRONTAL POSITION WILL
LIKELY LAG RESIDUAL CONVECTIVE OUTFLOWS ACROSS THESE AREAS. POCKETS
OF STRONG DIURNAL HEATING OF VERY MOIST AIR MASS SHOULD CONTRIBUTE
TO INCREASINGLY UNSTABLE CONDITIONS DEVELOPING AMIDST THE FRONTAL
ZONE AND VARIOUS OUTFLOW BOUNDARIES BENEATH 20-30KT MID LEVEL WLY
FLOW. DESPITE GENERALLY WEAKER LARGE SCALE SUPPORT FOR ASCENT ACROSS
THE FRONT...BOUNDARY INTERACTIONS...AND POSSIBLE SUPPORT FROM
EJECTING SHORT WAVE DISTURBANCE FORMERLY ASSOCIATED WITH T.S.
HENRIETTE...COULD SPUR SEVERAL TSTM CLUSTERS. MODEL GUIDANCE DEPICTS
AREAS OF MARGINALLY FAVORABLE EFFECTIVE SHEAR ACROSS THE REGION
SUGGESTING SOME WIND DAMAGE POTENTIAL FROM A FEW
ORGANIZED/PERSISTENT MULTICELL STORM CLUSTERS THROUGH THE PERIOD.
..MT...
FOCUSED QG-FORCING FOR ASCENT IS FORECAST TO ACCOMPANY THE
LOW-AMPLITUDE IMPULSE SPREADING SEWD ACROSS THE NRN ROCKIES DURING
THE AFTERNOON. STRENGTHENING LOW LEVEL UPSLOPE FLOW AND DIMINISHING
STATIC STABILITY SHOULD LEAD TO HIGH-BASED CONVECTIVE DEVELOPMENT
DESPITE SOMEWHAT MARGINAL LOW LEVEL MOISTURE. LEE-SIDE CYCLOGENESIS
ALONG TIGHTENING THERMAL GRADIENT ACROSS SCNTRL MT WILL FURTHER
SUPPORT POTENTIAL FOR A FEW ORGANIZED TSTMS WITH WIND AND HAIL
POTENTIAL. AT PRESENT...LIMITED DESTABILIZATION IS EXPECTED TO
INHIBIT MORE WIDESPREAD SEVERE WEATHER THREAT ACROSS THE AREA.
.CARBIN/GRAMS.. 09/07/2007
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