DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 200540
SWODY1
SPC AC 200537

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1137 PM CST WED DEC 19 2007

VALID 201200Z - 211200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE CENTRAL
GULF STATES...

..GULF COAST...

LATE EVENING WV IMAGERY SUPPORTS 00Z MODEL GUIDANCE REGARDING THE
POSITION/MOVEMENT OF SRN STREAM UPPER SHORTWAVE TROUGH. TROUGH AXIS
IS VERY NEAR THE NM/TX BORDER ATTM AND THIS FEATURE SHOULD MOVE
ACROSS TX THROUGH THE GULF COAST STATES INTO SRN GA BY THE END OF
THE PERIOD. WARM ADVECTION CONVECTION HAS RECENTLY DEVELOPED
DOWNSTREAM ACROSS SERN TX INTO SRN AR AS LLJ INCREASES ACROSS THIS
REGION. LATEST THINKING IS MODIFIED GULF AIRMASS WILL RETURN INLAND
ACROSS THE LOWER MS VALLEY THIS MORNING WITH 60S DEW POINTS EXPECTED
AS FAR NORTH AS PORTIONS OF SCNTRL AR BY SUNRISE. BOUNDARY LAYER
RECOVERY WILL PROVE INSTRUMENTAL IN DESTABILIZATION NECESSARY FOR
UPWARD GROWTH OF THUNDERSTORM CLUSTERS...LIKELY EVOLVING INTO AN MCS
OVER MS/AL AS LLJ VEERS TO A MORE WLY DIRECTION DURING THE DAYLIGHT
HOURS. AT THIS TIME IT APPEARS WARM ADVECTION WILL BE THE PRIMARY
DRIVING MECHANISM FOR DEEP CONVECTION ALONG SLOWLY RETREATING WARM
FRONT. IN THE WAKE OF THIS ACTIVITY LAPSE RATES WILL STEEPEN
SIGNIFICANTLY AS WLY FLOW DEEPENS THROUGH MID LEVELS. IT/S NOT
ENTIRELY CLEAR BASED ON THE AFOREMENTIONED CONVECTIVE SCENARIO
WHETHER SUFFICIENT CONVERGENCE WILL EXIST WITHIN STEEPER LAPSE
RATE/HIGHER INSTABILITY AIRMASS FOR MORE THAN ISOLATED THUNDERSTORM
DEVELOPMENT. IF ROBUST THUNDERSTORM ACTIVITY DOES EVOLVE IT MAY DO
SO ALONG LINGERING CONVECTIVE OUTFLOW BOUNDARIES...MOST LIKELY
ORIENTED IN AN E-W FASHION NEAR THE GULF COAST FROM SRN LA INTO SRN
MS. LARGE HAIL AND DAMAGING WINDS ARE THE PRIMARY SEVERE THREATS
GIVEN THE EXPECTED CLUSTERING NATURE AND THE LIKELIHOOD FOR MOST
CONVECTION TO OCCUR WITHIN WEAKER LAPSE RATE/INSTABILITY REGIME
ALONG RETREATING WARM FRONT. HOWEVER...SUFFICIENT SPEED SHEAR WILL
EXIST WITHIN MORE BUOYANT VEERED BOUNDARY LAYER FOR ROBUST ROTATING
UPDRAFTS IF MESOSCALE BOUNDARIES CAN SURVIVE INTO THE MID AFTERNOON
HOURS.

.DARROW.. 12/20/2007

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