Monday, December 8, 2008

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 090040
SWODY1
SPC AC 090037

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0637 PM CST MON DEC 08 2008

VALID 090100Z - 091200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SE OK...NORTH
AND EAST TX...NW LA AND SW AR...

...SRN PLAINS/ARKLATEX...
WATER VAPOR IMAGERY SHOWS A LARGE UPPER-LEVEL TROUGH OVER THE WRN
AND CNTRL U.S. WITH A WELL-DEVELOPED SHORTWAVE TROUGH EMBEDDED IN
THE BASE OF THE LARGE-SCALE TROUGH OVER SE NM. A PRONOUNCED DRY SLOT
IS EVIDENT ACROSS NRN MEXICO EXTENDING ENEWD INTO WCNTRL TX. A BAND
OF STRONG LARGE-SCALE ASCENT ANALYZED BY THE RUC IS LOCATED NORTH OF
THE DRY SLOT IN WEST TX AND THE TX PANHANDLE. AS THIS BAND OF LIFT
SPREADS QUICKLY EWD ACROSS NORTH TX AND SRN OK THIS
EVENING...SCATTERED THUNDERSTORMS SHOULD DEVELOP. THUNDERSTORMS
SHOULD INITIATE ALONG AN AXIS OF INSTABILITY CURRENTLY LOCATED WEST
OF DALLAS/FORT WORTH AND EXPAND IN COVERAGE MOVING ACROSS ERN OK AND
EAST TX INTO SW AR AND NW LA DURING THE OVERNIGHT PERIOD.

CONCERNING THE SEVERE POTENTIAL...WSR-88D VWPS SHOW A STRONGLY
SHEARED ENVIRONMENT ACROSS MOST OF THE REGION WITH 0-6 KM SHEAR
VALUES IN THE 50 TO 60 KT RANGE. THIS ALONG WITH INCREASING
LOW-LEVEL MOISTURE DUE TO A STRENGTHENING 45 TO 55 KT LOW-LEVEL JET
OVER EAST TX WILL MAKE ORGANIZED THUNDERSTORMS INCREASINGLY LIKELY
LATE THIS EVENING INTO THE OVERNIGHT PERIOD. CONVECTION APPEARS MOST
LIKELY TO INITIATE NEAR THE RED RIVER ALONG THE I-35 CORRIDOR AS
LARGE-SCALE ASCENT ERODES THE CAPPING INVERSION BETWEEN 03Z AND 06Z.
ALTHOUGH THE FORT WORTH 00Z SOUNDING SHOWS WEAK MID-LEVEL LAPSE
RATES...RUC ANALYSIS SUGGESTS MID-LEVEL LAPSE RATES ARE MUCH STEEPER
JUST WEST OF THE DALLAS/FORT WORTH METROPLEX. IF MORE INTENSE STORMS
CAN DEVELOP IN THE STEEPER MID-LEVEL LAPSE RATES...HAIL WOULD BE
LIKELY. HOWEVER...THE GREATER THREAT MAY EXIST AS STORMS MOVE EWD
AND BECOME MORE CLOSELY SFC-BASED ACROSS NE TX. SFC DEWPOINTS ARE
ALREADY IN THE UPPER 50S F IN THE DALLAS AREA AND LOWER 60S F
DEWPOINTS SHOULD MOVE NWD INTO THE ARKLATEX AFTER MIDNIGHT. THIS
ALONG WITH 0-1 KM SHEAR VALUES IN THE 35 TO 40 KT RANGE SHOULD
SUPPORT A ISOLATED TORNADO THREAT LATE TONIGHT. IN
ADDITION...ISOLATED WIND DAMAGE WILL BE POSSIBLE ESPECIALLY IF
PERSISTENT LINE-SEGMENTS CAN ORGANIZE.

..BROYLES.. 12/09/2008

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