SPC AC 190552
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1152 PM CST TUE DEC 18 2007
VALID 191200Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM ERN PORTIONS OF THE SRN
PLAINS EWD INTO THE LOWER MS VALLEY REGION...
...SYNOPSIS...
PROGRESSIVE MID-LEVEL FLOW PATTERN TO PERSIST ACROSS THE U.S. THIS
PERIOD...WITH SEVERAL SHORT-WAVE FEATURES FORECAST TO MOVE
RELATIVELY QUICKLY FROM W-E ACROSS THE CONUS. THE MAIN FEATURE IN
TERMS OF THE CONVECTIVE FORECAST WILL BE THE SHORT-WAVE TROUGH
INITIALLY EXTENDING N-S ACROSS THE ROCKIES AND INTO THE DESERT SW.
THIS FEATURE IS FORECAST TO SHIFT INTO THE PLAINS DURING THE SECOND
HALF OF THE PERIOD...ALONG WITH A WEAK/ACCOMPANYING SRN PLAINS
SURFACE CYCLONE AND AN INCREASING SSWLY LOW-LEVEL JET. RESULTING
NWD ADVECTION OF LOW-LEVEL MOISTURE INTO THE SRN PLAINS/LOWER MS
VALLEY SHOULD LEAD TO AN INCREASE IN THUNDERSTORM POTENTIAL THROUGH
THE SECOND HALF OF THE PERIOD.
...ERN TX INTO LA AND PARTS OF SWRN MS...
MARGINAL DESTABILIZATION IS FORECAST -- PARTICULARLY AFTER SUNSET --
FROM ERN PORTIONS OF THE SRN PLAINS INTO THE LOWER MS VALLEY...AS
SLY/SSWLY LOW-LEVEL FLOW ADVECTS MOISTURE NWD BENEATH STEEPER LAPSE
RATES SPREADING EWD WITHIN WLY FLOW ALOFT.
MOST OF THE THUNDERSTORM DEVELOPMENT -- LIKELY LIMITED PRIMARILY TO
THE SECOND HALF OF THE PERIOD -- SHOULD OCCUR ATOP A SHALLOW/MORE
STABLE SURFACE LAYER. HOWEVER...DEGREE OF INSTABILITY AND
MODERATE/VEERING FLOW WITH HEIGHT SHOULD BE SUFFICIENT FOR SOME
STORM ORGANIZATION/ROTATION. A FEW OF THE STRONGER STORMS MAY
PRODUCE MARGINAL HAIL...AND MODEST/SHALLOW NATURE OF THE STABLE
LAYER SUGGESTS AT LEAST A MINIMAL POTENTIAL FOR A COUPLE OF
SURFACE-BASED WIND GUSTS AT OR NEAR SEVERE LEVELS.
..GOSS.. 12/19/2007
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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