SWODY2
SPC AC 141730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1130 AM CST FRI DEC 14 2007
VALID 151200Z - 161200Z
..THERE IS A SLGT RISK OF SVR TSTMS LATE SAT AFTN/SAT NIGHT ACROSS
PARTS OF THE EASTERN GULF STATES....
..SYNOPSIS...
AN AMPLIFIED UPPER TROUGH CONTINUES TO EVOLVE ACROSS THE
INTERMOUNTAIN WEST/ROCKIES REGION...WITHIN A BELT OF STRONG POLAR
WESTERLIES EMANATING FROM THE NORTHERN PACIFIC. MODELS INDICATE
THAT THIS FEATURE WILL TURN EASTWARD INTO THE PLAINS BY 12Z
SATURDAY...BEFORE TAKING ON AN INCREASING NEGATIVE TILT AND LIFTING
EAST NORTHEASTWARD TOWARD THE ATLANTIC COAST...IN PHASE WITH A BELT
OF WESTERLIES EMANATING FROM THE SUBTROPICAL PACIFIC.
IN RESPONSE TO LARGE-SCALE FORCING WITH THE UPPER PATTERN...MODELS
INDICATE THAT THE SURFACE LOW...EXPECTED TO FORM ACROSS SOUTHEAST
TEXAS AND THE LOWER MISSISSIPPI VALLEY TONIGHT...WILL CONTINUE TO
DEEPEN AS AT LIFTS INTO/THROUGH THE TENNESSEE VALLEY AND MID/UPPER
OHIO VALLEY SATURDAY/SATURDAY NIGHT. AND...SIGNIFICANT SECONDARY
SURFACE CYCLOGENESIS IS EXPECTED TO INITIATE ALONG ANOTHER
STRENGTHENING FRONTAL ZONE FROM THE EASTERN GULF STATES THROUGH
SOUTHERN/MID ATLANTIC COASTAL AREAS.
A MODEST GULF MOISTURE RETURN IS EXPECTED THROUGH THE WARM SECTOR OF
THE INITIAL SURFACE CYCLONE...ACROSS MUCH OF LOUISIANA INTO
MISSISSIPPI/ALABAMA. BUT...A MUCH MORE SIGNIFICANT RETURN FLOW
SEEMS LIKELY ACROSS THE EASTERN GULF COAST THROUGH THE SOUTHERN/MID
ATLANTIC COAST STATES...WHERE MODELS SUGGEST THAT THE PRIMARY
SOUTHERLY LOW-LEVEL JET WILL DEVELOP LATE SATURDAY AFTERNOON INTO
SATURDAY NIGHT. THIS WILL BE ENHANCED BY AN INFLUX OF MOISTURE
ASSOCIATED WITH THE TROPICAL IMPULSE NOW APPROACHING THE YUCATAN
PENINSULA.
..SOUTHEAST STATES...
GIVEN A MOISTENING BOUNDARY LAYER THROUGH A SIZABLE PORTION OF THE
SOUTHEAST STATES...BENEATH STRENGTHENING AND INCREASINGLY CYCLONIC
MID/UPPER FLOW...WHICH WILL CONTRIBUTE TO STRONG DEEP LAYER SHEAR
SUPPORTIVE OF SUPERCELLS...SEVERE THUNDERSTORM POTENTIAL WILL EXIST
THROUGH THIS PERIOD. THE MAGNITUDE OF THIS THREAT IS STILL
UNCLEAR...PRIMARILY DUE TO CONSIDERABLE SPREAD AMONG MODEL DATA
CONCERNING THE SMALL SCALE DETAILS OF THE EVOLVING PATTERN...AND THE
LIKELIHOOD THAT WEAK MID-LEVEL LAPSE RATES WILL RESTRICT
DESTABILIZATION IN THE WARM SECTOR.
IN FACT...MOST MODEL GUIDANCE INDICATES ONLY VERY WEAK MIXED LAYER
CAPE INLAND OF COASTAL AREAS. AN EXCEPTION COULD BE ACROSS THE
FLORIDA PANHANDLE AND NORTHERN FLORIDA INTO SOUTHERN GEORGIA...AS
THE SOUTHERLY LOW-LEVEL JET BEGINS TO INTENSIFY LATE SATURDAY
AFTERNOON INTO SATURDAY EVENING. CAPE ON THE ORDER OF 500-1000 J/KG
APPEARS POSSIBLE. AND...LARGE CLOCKWISE CURVED HODOGRAPHS BENEATH
40-50 KT 850 MB FLOW...AS WELL AS A NEAR SATURATED BOUNDARY LAYER
AIR MASS CHARACTERIZED BY SURFACE DEW POINTS IN THE UPPER 60S...WILL
BE SUPPORTIVE OF SUPERCELLS WITH POTENTIAL FOR TORNADOES AND
DAMAGING WIND GUSTS. THIS THREAT COULD SHIFT FROM THE EASTERN GULF
STATES THROUGH THE SOUTHERN MID ATLANTIC STATES SATURDAY NIGHT.
BUT...UNCERTAINTIES CONCERNING SECONDARY SURFACE LOW
DEVELOPMENT/EVOLUTION SEEM TOO LARGE FOR A CATEGORICAL SEVERE
OUTLOOK ACROSS THE CAROLINAS AT THE PRESENT TIME.
UNCERTAINTIES...PRIMARILY WITH REGARD TO THE MAGNITUDE OF
INSTABILITY...ALSO PRECLUDE A CATEGORICAL SEVERE OUTLOOK AT THIS
TIME...NEAR THE TRACK OF THE INITIAL SURFACE LOW...FROM SOUTHEAST
LOUISIANA THROUGH CENTRAL MISSISSIPPI/NORTHERN ALABAMA LATE SATURDAY
MORNING THROUGH EARLY SATURDAY EVENING.
.KERR.. 12/14/2007
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