SWODY1
SPC AC 260602
DAY 1 CONVECTIVE OUTLOOK RESENT 1
NWS STORM PREDICTION CENTER NORMAN OK
1202 AM CST FRI DEC 26 2008
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN OK...NE
TX...WRN AR...SE KS AND MO...
...SRN PLAINS/OZARKS...
A WELL-DEVELOPED UPPER-LEVEL TROUGH OVER THE INTERMOUNTAIN WEST
TODAY WILL MOVE INTO THE ROCKIES TONIGHT. AHEAD OF THE SYSTEM...A 50
TO 60 KT LOW-LEVEL JET WILL BE IN PLACE FROM EAST TX EXTENDING NEWD
INTO THE MID-MS VALLEY. THIS FEATURE WILL RESULT IN RAPID MOISTURE
RETURN ACROSS THE SRN PLAINS AND OZARK REGION. SFC DEWPOINTS OF AT
LEAST 60 F APPEAR LIKELY TO OVERSPREAD MUCH OF ERN OK...AR AND SRN
MO BY THIS EVENING. AS LARGE-SCALE ASCENT INCREASES AHEAD OF THE
APPROACHING UPPER-LEVEL TROUGH...NUMEROUS THUNDERSTORMS SHOULD
DEVELOP ALONG THE WRN EDGE OF THE LOW-LEVEL JET FROM CNTRL MO SWWD
INTO NW AR...ERN OK AND EAST TX. ALTHOUGH MODEL FORECASTS DIFFER
SLIGHTLY ON THE TIMING AND LOCATION OF INITIATION...CONCENSUS PLACES
THE INITIAL DEVELOPMENT IN THE WARM SECTOR OVER NERN OK...SE KS AND
WRN MO AROUND 03Z THIS EVENING. THIS SEEMS REASONABLE WITH A RAPID
INCREASE IN COVERAGE ALONG THE INSTABILITY AXIS FROM NNE TO SSW
DURING THE OVERNIGHT PERIOD. ANOTHER BAND OF CONVECTION APPEARS
LIKELY TO ORGANIZE ALONG A COLD FRONT ADVANCING SEWD ACROSS CNTRL OK
AND NCNTRL TX DURING THE 08Z TO 12Z TIMEFRAME.
CONCERNING THE SEVERE POTENTIAL...THE ERN EDGE OF A BROAD 80 TO 100
KT MID-LEVEL JET WILL MOVE EWD ACROSS THE SRN HIGH PLAINS AND CNTRL
PLAINS TODAY AND INTO THE SRN PLAINS AND OZARKS DURING THE OVERNIGHT
PERIOD. THIS WILL GRADUALLY INCREASE VERTICAL SHEAR PROFILES ACROSS
THE REGION WITH TIME. 0-6 KM SHEAR VALUES SHOULD RANGE FROM 60 TO 75
KT BY 06Z ACROSS MUCH OF THE WARM SECTOR. IN ADDITION...NAMKF
FORECAST SOUNDINGS DEVELOP A NARROW AXIS OF MODERATE INSTABILITY
FROM NEAR DALLAS/FORT WORTH NEWD TO SOUTHWEST OF SPRINGFIELD MO.
THIS ALONG WITH THE STRONG VERTICAL SHEAR SHOULD SUPPORT SUPERCELL
DEVELOPMENT WITH THE GREATEST THREAT AT THE BEGINNING OF THE EVENT
WHEN STORMS WILL HAVE THE BEST CHANCE TO REMAIN DISCRETE. 0-1 KM
SHEAR VALUES OF 25 TO 30 KT SHOULD BE ENOUGH FOR A TORNADO THREAT
WITH SUPERCELLS THAT DEVELOP ESPECIALLY WEST OF THE LOW-LEVEL JET
ACROSS ERN OK...FAR NW AR AND FAR SW MO. AS STORM COVERAGE RAPIDLY
INCREASES...THE DOMINANT MODE MAY BECOME LINEAR INSTEAD OF MULTICELL
LINE-SEGMENTS AS A SQUALL-LINE ORGANIZES AFTER MIDNIGHT. THIS ALONG
WITH 30 TO 40 KT OF FLOW JUST ABOVE THE SFC MAY TRANSLATE TO A WIND
DAMAGE THREAT AS THE LINE INTENSIFIES LATE IN THE PERIOD. ALTHOUGH
THE SQUALL-LINE MAY HAVE A THREAT FOR HAIL...THE GREATER THREAT FOR
HAIL MAY EXIST AS STORMS DEVELOP ALONG A COLD FRONT IN CNTRL OK AND
NCNTRL TX LATE WHERE MID-LEVEL LAPSE RATES MAY BE A BIT STEEPER.
FURTHER SOUTH ACROSS CNTRL AND EAST TX...LARGE-SCALE ASCENT IS NOT
FORECAST TO BE AS STRONG. THIS MAY HOLD CONVECTIVE INITIATION BACK
UNTIL AROUND 12Z. IF CONVECTION CAN INITIATE BY THE END OF THE
PERIOD...THE COMBINATION OF STRONG VERTICAL SHEAR AND MODERATE
INSTABILITY EVIDENT ON FORECAST SOUNDINGS SHOULD BE SUPPORTIVE OF AT
LEAST A MARGINAL WIND DAMAGE OR HAIL THREAT.
..BROYLES.. 12/26/2008
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