DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 270100
SWODY1
SPC AC 270057

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0657 PM CST FRI DEC 26 2008

VALID 270100Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE SRN PLAINS
AND OZARKS...

...SRN PLAINS/OZARK PLATEAU...
A WELL-DEVELOPED UPPER-LEVEL TROUGH OVER THE FOUR CORNER REGION WILL
MOVE EWD ACROSS THE ROCKIES TONIGHT. AHEAD OF THE SYSTEM...A LARGE
50 TO 65 KT LOW-LEVEL JET WILL CONTINUE TO GRADUALLY STRENGTHEN OVER
THE OZARKS. THIS WILL SUSTAIN MOISTURE ADVECTION ACROSS A LARGE WARM
SECTOR. SFC ANALYSIS SHOWS DEWPOINTS IN THE LOWER TO MID 60S F
ACROSS MOST OF THE ERN HALF OF TX...ERN OK AND AR WITH RUC ANALYSIS
SUGGESTING UNSEASONABLY STRONG INSTABILITY EXISTS ACROSS ECNTRL OK.
AS LARGE-SCALE ASCENT INCREASES LATE THIS EVENING DUE TO THE
APPROACHING UPPER-LEVEL TROUGH...SCATTERED THUNDERSTORMS SHOULD
INITIATE ALONG THE INSTABILITY AXIS ACROSS WRN MO...SE KS AND NE OK
AND LATER ALONG THE COLD FRONT FURTHER WEST. THIS CONVECTION SHOULD
QUICKLY EXPAND IN COVERAGE FROM NNE TO SSW WITH SQUALL-LINE
DEVELOPMENT LIKELY BY 12Z ACROSS PARTS OF THE REGION.

CONCERNING THE SEVERE POTENTIAL...RUC ANALYSIS SHOWS 0-6 KM SHEAR
VALUES RANGING FROM AROUND 50 KT IN NORTHEAST TX TO ABOUT 65 KT IN
SE KS. THE VERTICAL SHEAR SHOULD GRADUALLY INCREASE AS A 80 TO 100
KT MID-LEVEL JET APPROACHES THE REGION FROM THE WEST. THIS ALONG
WITH THE AMOUNT OF INSTABILITY ALREADY IN PLACE SHOULD SUPPORT A
SEVERE THREAT SHORTLY AFTER STORMS INITIATE. FORECAST SOUNDINGS ON
THE WRN EDGE OF THE LOW-LEVEL JET SHOW SFC-3 KM SHEAR VALUES OF
ABOUT 400 M2/S2 SUGGESTING THE SHEAR ENVIRONMENT WILL BE FAVORABLE
FOR SUPERCELLS AND A FEW TORNADOES. THE GREATEST SUPERCELL THREAT
WITH POTENTIAL MAY OCCUR NEAR THE ONSET OF THE EVENT IN THE 05Z TO
10Z TIME FRAME WHEN STORMS WILL MORE LIKELY BE DISCRETE. THE
GREATEST TORNADO THREAT SHOULD EXIST WITH SUPERCELLS CLOSER TO THE
LOW-LEVEL JET OVER ERN OK WHERE DEWPOINTS ARE ABOVE 60 F AND 0-1 KM
SHEAR VALUES SHOULD BE AROUND 35 KT LATE TONIGHT. AN ISOLATED STRONG
TORNADO COULD OCCUR IF A SUPERCELL CAN BECOME DOMINANT TO THE EAST
OF A DEVELOPING SQUALL-LINE. AS THIS SQUALL-LINE ORGANIZES FROM
CNTRL MO SSWWD ACROSS ECNTRL OK INTO NE TX VERY LATE IN THE
PERIOD...THE WIND DAMAGE THREAT SHOULD INCREASE. FORECAST SOUNDINGS
ALONG THIS CORRIDOR SHOW 40 TO 50 KT AT ABOUT 1 KM ABOVE THE
SFC...SUGGESTING THE WIND DAMAGE THREAT COULD BECOME MORE WIDESPREAD
IF THE SQUALL-LINE CAN EFFECTIVELY TRANSPORT THE STRONGER WINDS TO
THE SFC.

FURTHER SOUTH ACROSS ECNTRL TX...LARGE-SCALE ASCENT WILL BE WEAKER
AND A CAPPING INVERSION SHOULD EFFECTIVELY HOLD OFF CONVECTIVE
DEVELOPMENT UNTIL VERY LATE IN THE PERIOD. IF STORMS CAN INITIATE BY
12Z...FORECAST SOUNDINGS JUST SOUTH OF THE DALLAS/FORT WORTH AREA
SUGGEST THE SHEAR AND INSTABILITY ENVIRONMENT SHOULD BE SUPPORTIVE
OF ISOLATED WIND DAMAGE AND HAIL. SOUTH FROM THERE...THE CONVECTIVE
POTENTIAL IS MUCH LOWER SUGGESTING A SEVERE THREAT WILL BE HIGHLY
CONDITIONAL.

..BROYLES.. 12/27/2008

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