SPC AC 130536
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1236 AM CDT TUE MAY 13 2008
VALID 141200Z - 151200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM TX/SERN OK INTO THE LOWER
MS VALLEY...
...SRN PLAINS/LOWER MS VALLEY...
00Z MODEL GUIDANCE IS IN GENERAL AGREEMENT WITH LARGE SCALE FEATURES
THROUGH THE DAY2 PERIOD. UPPER LOW ALONG THE NM/MEXICO BORDER WILL
FINALLY EJECT EWD INTO WEST TX DURING THE DAY WITH FAIRLY STRONG
MID-HIGH LEVEL FLOW FORECAST TO OVERSPREAD THE SRN
PLAINS...ESPECIALLY TX. ADDITIONALLY...QUITE COLD THERMAL TROUGH
WILL ACCOMPANY THIS FEATURE WITH H5 TEMPERATURES EXPECTED TO
APPROACH MINUS 18C BENEATH THE UPPER LOW AND VALUES NEAR MINUS 12
ALONG THE DRYLINE AT 15/00Z.
IN ADDITION TO STRENGTHENING DEEP LAYER SHEAR...PRECIPITABLE WATER
VALUES WILL INCREASE MARKEDLY ACROSS TX INTO THE LOWER MS VALLEY.
FORECAST SOUNDINGS AGREE THAT UPWARDS OF 1.75-2 INCHES COULD EASILY
OVERSPREAD MUCH OF THE WARM SECTOR EAST OF I-35. GIVEN THIS
INCREASE IN MOISTURE THERE IS SOME CONCERN THAT DAY1 CONVECTION
COULD UTILIZE HIGHER BUOYANCY AND WEAKEN LAPSE RATES ACROSS MUCH OF
THE OUTLOOK REGION. NAM GUIDANCE DEFINITELY SUGGESTS THIS IS A REAL
POSSIBILITY WHILE GFS IS MORE AGGRESSIVE WITH INSTABILITY OWING TO
A MUCH WARMER BOUNDARY LAYER...ESPECIALLY THAT REGION NEAR THE
DRYLINE. IT'S NOT ENTIRELY CLEAR OF THE CONVECTIVE EVOLUTION DURING
THE DAY2 PERIOD AS HIGH QUALITY MOISTURE WILL LIKELY RESULT IN ONE
OR MORE ROGUE MCS-TYPE THUNDERSTORM CLUSTERS...MOST LIKELY NOT
HANDLED WELL BY THE MODEL GUIDANCE. HOWEVER...A BIT MORE CONFIDENCE
EXISTS FOR THUNDERSTORM DEVELOPMENT ALONG THE DRYLINE BY MID-LATE
AFTERNOON. INITIAL SUPERCELL STRUCTURES SHOULD ORGANIZE INTO
CLUSTERS AS DEEP LAYER SHEAR WILL BE MORE THAN ADEQUATE FOR HIGH
LEVEL VENTING...WHILE LOW LEVEL FLOW IS NOT EXPECTED TO BE THAT
STRONG THROUGH EARLY EVENING. ALTHOUGH...DURING THE OVERNIGHT HOURS
LLJ SHOULD STRENGTHEN ACROSS NERN TX INTO THE LOWER MS VALLEY. THIS
WILL LIKELY ENHANCE AN UPWARD EVOLVING MCS NEAR THE RED RIVER WHICH
WILL SPREAD INTO AR AND WRN TN BY SUNRISE. IF A REASONABLY PRISTINE
BOUNDARY LAYER CAN BE SUSTAINED ACROSS TX THERE WILL CERTAINLY BE A
RISK FOR MORE SIGNIFICANT WIDESPREAD SEVERE THUNDERSTORM
DEVELOPMENT. A MODERATE RISK MAY ULTIMATELY BE REQUIRED ACROSS MUCH
OF THIS REGION.
..DARROW.. 05/13/2008
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z
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