SPC AC 311728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CST FRI DEC 31 2010
VALID 011200Z - 021200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A DEEP CLOSED LOW CENTERED OVER THE UPPER MIDWEST AT THE START OF
DAY 2 /NEW YEARS DAY/ IS EXPECTED TO UNDERGO FURTHER DEEPENING AS
THIS SYSTEM BECOMES NEGATIVELY-TILTED AND EXTENDS FROM NRN ONTARIO
TO SRN QUEBEC BY 12Z SUNDAY. THE MEAN LONGWAVE TROUGH OVER THE
CENTRAL CONUS WILL SHIFT SLOWLY EWD AS AN UPSTREAM SHORTWAVE TROUGH
TRACKS SEWD FROM THE NRN ROCKIES TO THE CENTRAL PLAINS ON DAY
2...AND ADDITIONAL IMPULSES DIG SSEWD THROUGH CENTRAL CANADA TOWARD
THE N CENTRAL STATES. A COLD FRONT ATTENDANT TO THE PRIMARY UPPER
SYSTEM IS EXPECTED TO EXTEND FROM THE CENTRAL GREAT LAKES SSWWD
THROUGH THE OH/TN VALLEYS TO THE LOWER MS VALLEY AT 12Z SATURDAY.
THIS BOUNDARY WILL MOVE EWD AND OFF THE NRN ATLANTIC COAST BY 12Z
SUNDAY...WHILE THE SRN EXTENT STRETCHES SWWD THROUGH THE SERN STATES
TO CENTRAL GULF.
...CENTRAL GULF STATES...
AT 12Z SATURDAY...SHOWERS/EMBEDDED TSTMS ARE EXPECTED TO BE ONGOING
ALONG THE COLD FRONT FROM THE UPPER OH/TN VALLEYS TO THE LOWER MS
VALLEY AND INTO THE GULF OF MEXICO. ADDITIONAL CONVECTION SHOULD
ALSO BE ONGOING INVOF A PRE-FRONTAL LOW LEVEL CONFLUENCE ZONE
EXTENDING FROM THE NORTH CENTRAL GULF INTO SWRN AL.
STRONGEST FORCING FOR ASCENT IS EXPECTED TO REMAIN WELL NORTH OF
THIS REGION AS A COUPLE OF SHORTWAVE TROUGHS TRACK NEWD FROM THE
UPPER MS VALLEY AND CENTRAL PLAINS INTO ERN CANADA. NEUTRAL-VERY
WEAK HEIGHT FALLS ARE FORECAST ACROSS THE CENTRAL GULF COAST STATES
ON NEW YEARS DAY WITH MID-UPPER LEVEL WINDS INCREASING OVER THIS
REGION AS THE SRN EXTENT OF THE POLAR JET TRANSLATES NEWD FROM THE
LOWER MS VALLEY TO THE MID ATLANTIC STATES. MODELS INDICATED A SWLY
LLJ WILL LIKELY STRENGTHEN /50-60 KT/ FRIDAY NIGHT/EARLY SATURDAY
MORNING ALONG AND W OF THE SRN/CENTRAL APPALACHIANS FROM AL TO
OH...WITH THE SRN EXTENT OF THIS LLJ HAVING SPEEDS UP TO 40 KT ALONG
THE N CENTRAL GULF COAST. HOWEVER...THE GULF COAST PORTION OF THE
LLJ IS EXPECTED TO VEER AND WEAKEN GREATLY BY SATURDAY AFTERNOON AS
THIS JET MOVES NEWD ACROSS THE CENTRAL APPALACHIANS.
SLY LOW LEVEL WINDS WILL MAINTAIN A MOIST BOUNDARY LAYER DURING THE
FIRST HALF OF THE PERIOD ACROSS THE WARM SECTOR. HOWEVER...LIMITED
SURFACE HEATING DUE TO EXISTING PRECIPITATION/CONVECTIVE CLOUDINESS
ALONG AND AHEAD OF THE COLD FRONT AND WEAK LAPSE RATES SHOULD
GREATLY MINIMIZE INLAND INSTABILITY VALUES. THIS OUTLOOK WILL
MAINTAIN LOW SEVERE WEATHER PROBABILITIES FOR STORMS DURING THE
FIRST HALF OF THE PERIOD THAT MAY BE ABLE TO ATTAIN LOW LEVEL STORM
ROTATION/ISOLATED TORNADO THREAT AND/OR DAMAGING WINDS. HOWEVER...
EVENTUAL WEAKENING OF LOW LEVEL WINDS BY SATURDAY AFTERNOON AND WEAK
EFFECTIVE BULK SHEAR WILL FURTHER REDUCE THE SEVERE WEATHER THREAT.
..PETERS.. 12/31/2010
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z
|