SWODY3
SPC AC 130732
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0132 AM CST TUE DEC 13 2011
VALID 151200Z - 161200Z
...SYNOPSIS...
DISCREPANCIES AMONG THE MODELS CONTINUE...AND APPEAR TO INCREASE
DURING THIS PERIOD...CONCERNING THE SMALLER SCALE DEVELOPMENTS
WITHIN THE PREVAILING SPLIT UPPER FLOW PATTERN. IN GENERAL...
THOUGH...IT APPEARS THAT A LARGE SURFACE CYCLONE WILL CONTINUE TO
DEEPEN AS IT MIGRATES ACROSS EASTERN CANADA...IN ASSOCIATION WITH
CONSOLIDATING SOUTHERN AND NORTHERN STREAM IMPULSES. A TRAILING
SURFACE FRONT IS EXPECTED TO ADVANCE ACROSS THE LOWER GREAT LAKES
AND OHIO VALLEY...THROUGH THE NORTHERN/MID ATLANTIC COAST REGION AND
SOUTHERN APPALACHIANS...WHILE GRADUALLY STALLING ACROSS PARTS OF THE
TENNESSEE VALLEY INTO THE WESTERN GULF COAST REGION. THIS SHOULD
OCCUR AS ANOTHER VIGOROUS CLOSED LOW DIGS TO THE EAST OF AN EASTERN
PACIFIC UPPER RIDGE...INTO BROADER SCALE SOUTHERN BRANCH TROUGHING
OVER THE SOUTHWESTERN STATES. ALTHOUGH WEAKENING ...GUIDANCE
INDICATES THAT A MOIST RETURN FLOW WILL CONTINUE OFF THE GULF OF
MEXICO INTO THE VICINITY OF THE STALLING FRONT...WHERE SUFFICIENT
DESTABILIZATION MAY OCCUR FOR SCATTERED THUNDERSTORM ACTIVITY
THURSDAY/THURSDAY NIGHT.
...UPPER PORTIONS OF THE LWR MS VALLEY INTO THE TN VALLEY...
DESPITE THE PRESENCE OF HIGH PRECIPITABLE WATER UP TO AROUND 2
STANDARD DEVIATIONS ABOVE AVERAGE FOR MID DECEMBER...FORECAST
SOUNDINGS SUGGEST THAT LAPSE RATES WILL NOT STEEPEN SUFFICIENTLY TO
SUPPORT ANYTHING BEYOND VERY WEAK CAPE ALONG AND SOUTHEAST OF THE
FRONT. HOWEVER...THIS INSTABILITY MAY BE VERY NEARLY SURFACE BASED
DURING THE MID DAY AND AFTERNOON HOURS...PARTICULARLY ACROSS PARTS
OF NORTHERN MISSISSIPPI/ALABAMA AND ADJACENT SOUTHERN TENNESSEE.
AND IT APPEARS THAT STRONGLY SHEARED WEST SOUTHWESTERLY DEEP LAYER
MEAN FLOW COULD REMAIN STRONG ENOUGH /30-40+ KT/ TO SUPPORT AT LEAST
LOW PROBABILITIES FOR CONVECTION CAPABLE OF PRODUCING POTENTIALLY
DAMAGING WIND GUSTS.
..KERR.. 12/13/2011
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