SWODY2
SPC AC 241723
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1223 PM CDT SAT OCT 24 2009
VALID 251200Z - 261200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
PREVALENT LONGWAVE TROUGH OVER MUCH OF THE CONUS WILL BE REINFORCED
BY MULTIPLE SHORTWAVE PERTURBATIONS CROSSING THE NORTHERN
ROCKIES/WESTERN CANADA...AS A DISTINCT SOUTHERN STREAM SPLIT BEGINS
TO EVOLVE SUNDAY NIGHT INTO MONDAY OVER THE SOUTHERN
ROCKIES/SOUTHERN HIGH PLAINS. ASSOCIATED SHARPENING SURFACE FRONT
WILL ADVANCE EAST-SOUTHEASTWARD ACROSS THE MIDWEST AND
CENTRAL/SOUTHERN PLAINS THROUGH THE PERIOD. THIS FRONT WILL SERVE AS
THE PRIMARY FOCUS FOR DEEP CONVECTIVE POTENTIAL...MAINLY ACROSS THE
SOUTHERN PLAINS DURING THE LATTER HALF OF THE PERIOD SUNDAY
EVENING/NIGHT. COOL/STABLE CONDITIONS WILL OTHERWISE LARGELY LIMIT
TSTM POTENTIAL...PERHAPS ASIDE FROM SOUTH FL AND/OR NORTHEAST NM
WHERE SOME TSTMS WILL BE POSSIBLE.
...SOUTHERN/EASTERN OK AND MUCH OF TX LATE AFTERNOON/NIGHT...
WITH THE PRIOR FRONT/ASSOCIATED MOISTURE-RICH TROPICAL AIRMASS
CONFINED TO THE SOUTHERN GULF OF MEXICO/BAY OF CAMPECHE AT THIS
TIME...DETAILS OF SUNDAYS FORECAST SCENARIO CONTINUE TO LARGELY
HINGE ON THE POTENTIAL QUICK NORTHWARD RETURN OF A MODIFIED/MODESTLY
MOIST AIRMASS ACROSS TX/SOUTHERN OK AHEAD OF THE APPROACHING PLAINS
COLD FRONT. AS THE UPSTREAM SHORTWAVE TROUGH DEVELOPS OVER THE
SOUTHERN HIGH PLAINS DURING THE AFTERNOON/NIGHT...SREF DPROG/DT
TRENDS/MAJORITY OF MEMBERS DO SUPPORT A GRADUALLY INCREASING
CONFIDENCE THAT AROUND 60 F SURFACE DEWPOINTS WILL DEVELOP NORTHWARD
TO AROUND THE RED RIVER VICINITY AHEAD OF THE COLD FRONT/EAST OF A
DRYLINE BY LATE SUNDAY AFTERNOON. WITH A MOISTENING BOUNDARY LAYER
AND AMPLE DEEP LAYER/LOW LEVEL SHEAR ACROSS THE WARM SECTOR/FRONTAL
VICINITY...A MULTI-HOUR WINDOW OF QUASI-DISCRETE/SURFACE BASED
STORMS COULD OCCUR ALONG/JUST AHEAD OF THE FRONT LATE IN THE
AFTERNOON/EARLY EVENING MAINLY ACROSS NORTH CENTRAL TX...INCLUDING
THE POSSIBILITY OF SEVERE WIND/HAIL AND PERHAPS A TORNADO.
HOWEVER...IT APPEARS THAT MARGINAL MOISTURE/WARM SECTOR CAPPING
SHOULD CONFINE MUCH OF THE DEEP CONVECTIVE DEVELOPMENT TO THE
IMMEDIATE SURFACE FRONTAL ZONE TOWARD/AFTER DARK...AND THAT A
TENDENCY FOR FRONTAL UNDERCUTTING SHOULD TEMPORALLY LIMIT SUCH A
SURFACE BASED SEVERE THREAT /ALONG WITH A NOCTURNALLY COOLING
BOUNDARY LAYER/. WHILE A CATEGORICAL SLIGHT RISK MAY ULTIMATELY BE
WARRANTED...WILL DEFER TO SUBSEQUENT OBSERVATIONAL TRENDS/NUMERICAL
GUIDANCE GIVEN THE UNCERTAINTY REGARDING MOISTURE RETURN
TIMING/QUALITY AND EXPECTATIONS FOR A PRIMARY POST-SUNSET SEVERE
RISK.
..GUYER.. 10/24/2009
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