SWODY1
SPC AC 280043
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0643 PM CST SAT DEC 27 2008
VALID 280100Z - 281200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE WRN TN/OH VALLEYS...
...WRN TN NWD INTO THE WRN OH VALLEY...
AT EARLY EVENING...AN INTENSE AND FAST MOVING UPPER TROUGH WAS
TRACKING NEWD ACROSS NWRN MO...WITH A 110 KT MID LEVEL JET LOCATED
ON THE EAST SIDE OF THE SYSTEM FROM SWRN MO INTO ERN IA. THE UPPER
TROUGH WAS AIDING IN THE MAINTENANCE OF A SQUALL LINE FROM CENTRAL
IND SWWD INTO WRN TN. ONLY WEAK INSTABILITY WAS LOCATED AHEAD OF THE
LINE...WITH MUCAPES RANGING FROM 100 J/KG OVER INDIANA TO AROUND
1000 J/KG IN WRN TN. WHILE THE LARGE SCALE FORCING AND STRONG
ENVIRONMENTAL WINDS SHOULD SUPPORT PRIMARILY DAMAGING WINDS FOR THE
NEXT FEW HOURS...THE THREAT SHOULD GRADUALLY DIMINISH THROUGH THE
OVERNIGHT HOURS AS THE STRONGER FORCING SHIFTS NWD AND THE SQUALL
LINE GRADUALLY MOVES INTO WEAKER INSTABILITY. AN ISOLATED TORNADO IS
ALSO POSSIBLE WITHIN THE LINE...ESPECIALLY ACROSS WRN KY...GIVEN 1
SRH VALUES AROUND 500 M2/S2. HOWEVER...THE WEAKENING INSTABILITY
SUGGESTS ANY TORNADO OCCURRENCE WILL BE SHORT-LIVED.
...LOWER MS VALLEY...
THUNDERSTORMS CONTINUE IN A BAND FROM THE MS RIVER SWWD INTO FAR
SERN TX. WHILE MUCAPES FROM 500-1000 J/KG AND EFFECTIVE SHEAR NEAR
40 KT ARE FAVORABLE FOR SEVERE STORMS...THE MAIN UPPER SUPPORT HAD
LIFTED WELL NORTH OF THIS AREA. ALSO THIS AREA WAS LOCATED ON THE
ANTICYCLONIC SIDE OF THE JET...WHICH WAS RESULTING IN A WARM LAYER
BETWEEN 750-700 MB PER JAN/LCH SOUNDINGS. THE FACTORS ABOVE SHOULD
LIMIT THE SEVERE THREAT TO NO MORE THAN AN ISOLATED STORM OR TWO.
..IMY.. 12/28/2008
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