[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 131630
SWODY1
SPC AC 131628

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1028 AM CST SAT JAN 13 2007

VALID 131630Z - 141200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
QUASI-STATIONARY UPPER LOW OVER THE GREAT BASIN IS EXPECTED TO BEGIN
MOVING ESEWD TODAY AND REACH THE FOUR-CORNERS REGION BY LATE TONIGHT
IN RESPONSE TO UPSTREAM SHORT WAVE TROUGH DROPPING SSEWD ACROSS THE
PACIFIC NW.  AT THE SURFACE...COLD FRONT EXTENDS FROM A WEAK LOW
NEAR TXK SWWD THEN WWD ACROSS SOUTH CENTRAL TX...WITH A
QUASI-STATIONARY FRONT NEWD FROM THE LOW INTO THE LOWER OH VALLEY. 
THE LOW IS FORECAST TO MOVE SLOWLY NEWD ALONG THE QUASI-STATIONARY
FRONT AS THE TRAILING COLD FRONT MOVES SWD/SEWD ACROSS SERN/SOUTH
CENTRAL TX THROUGH TONIGHT.

...SOUTH CENTRAL TX...
SEVERAL NNE-SSW ORIENTED BANDS OF THUNDERSTORMS HAVE BEEN DEVELOPING
OVER SOUTH CENTRAL TX SOUTH OF THE COLD FRONT WITH STORMS
INTENSIFYING AS THEY CROSS THE FRONT AND MOVE NWD INTO A REGION OF
ELEVATED INSTABILITY.  THE CONVECTION MAY BE ASSOCIATED WITH
INCREASED DYNAMIC FORCING AS A MID/UPPER LEVEL PERTURBATION EVIDENT
IN WATER VAPOR IMAGERY MOVES NEWD TOWARD SWRN TX...WITH MESOSCALE
ASCENT ENHANCED BY PERSISTENT LOW LEVEL WARM ADVECTION/ISENTROPIC
LIFT ALONG/NORTH OF THE FRONT.  SURFACE AIR MASS WITHIN WARM SECTOR
IS WARM/MOIST WITH TEMPERATURES IN THE UPPER 60S/LOWER 70S AND DEW
POINTS IN THE MID/UPPER 60S...RESULTING IN MLCAPE OF 500-1000 J/KG. 
ELEVATED INSTABILITY WITH MUCAPE OF 200-500 J/KG EXTENDS TO THE
NORTH/NORTHWEST OF THE SURFACE FRONT.

EXTENSIVE CLOUDS ARE EXPECTED TO INHIBIT DIABATIC HEATING THIS
AFTERNOON...ALTHOUGH VISIBLE IMAGERY SHOWS SOME BREAKS IN CLOUD
COVER CLOSER TO THE RIO GRANDE WHERE A FEW AREAS OF STRONGER
HEATING/DESTABILIZATION MAY OCCUR.  MODERATELY STRONG SWLY FLOW
ALOFT WILL MAINTAIN SUFFICIENT DEEP LAYER SHEAR /35-45 KT IN THE
LOWEST 6 KM/ TO ENHANCE STORM ORGANIZATION AND
INTENSITY...SUGGESTING POTENTIAL FOR ISOLATED SEVERE STORMS TO OCCUR
THROUGH THIS AFTERNOON INTO THE EVENING.  THIS THREAT MAY BE LOCALLY
INCREASED NEAR THE FRONT WHERE VERTICAL SHEAR WILL BE
ENHANCED...SUGGESTING THREAT FOR A BRIEF TORNADO IN ADDITION TO
MARGINAL HAIL OR STRONG WIND GUSTS.  HOWEVER...STORMS ARE EXPECTED
TO QUICKLY BECOME ELEVATED AS THEY MOVE NORTH OF THE FRONT.
ADDITIONAL ELEVATED THUNDERSTORMS ARE EXPECTED TO DEVELOP LATER
TONIGHT NORTH OF THE FRONT OVER PARTS OF WEST CENTRAL INTO CENTRAL
TX AS LOW LEVEL JET DEVELOPS WWD INTO TX IN ASSOCIATION WITH THE
UPPER LOW MOVING INTO THE FOUR-CORNERS REGION.  MARGINAL HAIL MAY
OCCUR WITH ISOLATED STORMS.

...SERN TX INTO SRN AR...
A NARROW AXIS OF INSTABILITY IS IN PLACE ALONG AND IMMEDIATELY AHEAD
OF THE FRONT FROM SERN TX INTO SRN AR.  VISIBLE IMAGERY SHOWS BREAKS
IN CLOUD COVER FROM EAST CENTRAL TX INTO NORTH CENTRAL LA WHERE
DIURNAL HEATING WILL BE ENHANCED.  HOWEVER...LAPSE RATES ARE
EXPECTED TO REMAIN WEAK WHICH WILL LIMIT MLCAPE TO AOB 500 J/KG. 
12Z NAM AND ETAKF CONTROL MEMBER FROM THE 09Z SREF INDICATE NEW
CONVECTION DEVELOPING ALONG THE FRONT THIS AFTERNOON INTO THE
EVENING WITHIN LOW CAPE/HIGH SHEAR ENVIRONMENT.  THIS SUGGESTS
THREAT FOR AN ISOLATED SEVERE STORM OR TWO TO DEVELOP...BUT WEAK
INSTABILITY AND LIMITED FORCING FOR ASCENT SHOULD LIMIT OVERALL
SEVERE POTENTIAL.

..WEISS.. 01/13/2007