000
FXUS62 KGSP 061801
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
101 PM EST FRI DEC 6 2013

.SYNOPSIS...
MOIST SOUTHWESTERLY FLOW OFF THE GULF OF MEXICO WILL PERSIST ACROSS
THE REGION TODAY BEFORE A COLD FRONT SLOWLY CROSSES THE FORECAST
AREA SATURDAY. A COLD CANADIAN HIGH PRESSURE WILL THEN BUILD IN FROM
THE NORTHEAST SUNDAY WITH MOIST SOUTHERLY FLOW ALOFT CONTINUING INTO
MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
1800 UTC UPDATE...POPS WERE LOWERED EVERYWHERE BUT ALONG THE TN
BORDER PER RADAR AND SATELLITE TRENDS.

AT 0930 EST FRIDAY...A HIGH AMPLITUDE RIDGE WAS LOCATED OFF THE EAST
COAST....WHILE A TROUGH WAS LOCATED OVER THE ROCKIES. A 130KT UPPER
JET MAX WAS LOCATED BETWEEN THESE TWO FEATURES FROM TX TO QUEBEC. A
STRONG...SLOW MOVING COLD FRONT WAS LOCATED FROM FROM THE MID
ATLANTIC COAST...ALONG THE SOUTHERN APPALACHIANS...TO THE LOWER MS
RIVER VALLEY. DEW POINTS OVER 60 DEGREES WERE WIDESPREAD EAST OF
THIS FRONT...WHILE 70 DEGREE DEW POINTS WERE LIMITED TO THE GULF
COAST.

MODEST ELEVATED CAPE IS EXPECTED OVER THE MOUNTAINS TODAY. ALTHOUGH
THE BEST SHEAR EXISTS BENEATH THE THE UNSTABLE LAYER...ENOUGH SHEAR
EXISTS ALOFT FOR SOME CONCERN ABOUT ROTATING CELLS...AND SEVERE
WEATHER CANNOT BE RULED OUT. ANOTHER CONCERN IS THAT WIND SPEEDS
ALOFT WOULD SUPPORT DAMAGING WINDS IN STRONGER DOWNDRAFTS.

WITH VERY LIMITED ISENTROPIC UPGLIDE...THE BEST CHANCE FOR
PRECIPITATION WILL BE NEAREST THE FRONT IN THE MOUNTAINS...WHERE A
MARGINAL UPSLOPE FLOW COMPONENT WILL BE PRESENT WITH SW LOW LEVEL
FLOW. PRECIPITATION WILL BE SOMEWHAT LIMITED BY THE LESS THAN
ORTHOGONAL DIRECTION OF THE FLOW.

NEAR RECORD WARM MINIMUM TEMPERATURES WERE OBSERVED THIS MORNING.
MAXIMUMS TEMPERATURES ARE EXPECTED TO RISE INTO THE 70S EAST OF THE
MOUNTAINS...AND THE 60S IN THE MOUNTAINS...AS WARM ADVECTION
CONTINUES IN ADVANCE OF THE FRONT.

TONIGHT...POPS WILL GRADUALLY INCREASE TO THE EAST THROUGHOUT THE
EVENING HOURS AS THE FRONT SLOWLY PROGRESSES ACROSS THE REGION
OVERNIGHT INTO SATURDAY MORNING.  TEMPERATURES WITH THIS SYSTEM
REMAIN TOO WARM FOR ANY WINTRY PRECIPITATION IN THE NEAR TERM AS
MOISTURE EXITS BEFORE THE SUPPORTIVE COLD TEMPERATURES ENTER. LOWS
ON SATURDAY MORNING WILL BE IN THE UPPER 30S TO LOWER 40S ACROSS THE
NORTHERN MOUNTAINS WITH DECREASING TEMPERATURES TO THE SOUTHEAST
WHERE LOWER TO MID 50S WILL PREVAIL.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
AS OF 300 AM EST FRIDAY...THE SURFACE COLD FRONT AT THE LEADING EDGE
OF THE ARCTIC AIRMASS INVADING MUCH OF THE CONUS WILL GRADUALLY
SETTLE SE OF THE OUR FORECAST AREA SAT MORNING. MEANWHILE...DEEP
LAYER MOIST SW FLOW WILL PERSIST ACROSS THE REGION ALOFT AS A
POSITIVE TILT UPPER TROUGH DIGS THROUGH THE ROCKIES. THIS WILL KEEP
CHC POPS WEST TO LIKELY POPS EAST THROUGH SAT MORNING...WITH RAIN
CHANCES DIMINISHING THROUGH THE AFTERNOON AS SLIGHTLY DRIER AIR
FILTERS IN BEHIND THE FRONT FROM THE NW.

THE REPRIEVE WILL BE SHORT LIVED...HOWEVER...AS UPGLIDE MOISTURE
WILL GET STARTED AGAIN VERY QUICKLY SAT NIGHT AS UPPER HEIGHTS FALL
TO THE WEST. IN ADDITION...SPRAWLING SFC HIGH PRES STRETCHING FROM
THE GREAT LAKES THROUGH NEW ENGLAND WILL PROVIDE A FAVORABLE SOURCE
OF LOW LEVEL DRY AND COLD ADVECTION TO PRODUCE FAIRLY DEEP COLD AIR
DAMMING EAST OF THE APPALACHIANS BY DAYBREAK SUNDAY. THE STRONGEST
ISENTROPIC LIFT OVER THE STRENGTHENING CAD LAYER WILL LIKELY BE
ACROSS WESTERN NC FROM 12Z TO AT LEAST 18Z ON SUNDAY. DESPITE SOME
THERMAL PROFILE DIFFERENCES AMONG THE MODELS...THERE IS REASONABLE
CONSENSUS ON A PROMINENT WARM LAYER ALOFT...BUT WITH SUBFREEZING SFC
WET BULB TEMPERATURES AT ONSET ALONG AND NORTH OF THE INTERSTATE 40
CORRIDOR SAT NIGHT/EARLY SUNDAY. THESE FREEZING TEMPS COULD WELL GET
LOCKED IN THROUGH MUCH OF THE DAY ON SUNDAY ACROSS THE NRN BLUE
RIDGE AREA...AND THE IMMEDIATELY ADJACENT NRN NC FOOTHILLS. IN
COLLABORATION WITH WFO RNK...A WINTER STORM WATCH WILL BE POSTED FOR
A SMALL PORTION OF THE NRN TIER OF OUR FORECAST AREA FOR LATE
SATURDAY NIGHT THROUGH SUNDAY.

WAVES OF LOW PRES RIDING NWD ALONG THE TRAILING COLD FRONT WILL
BRING HEAVY RAIN INTO THE APPALACHIANS SUNDAY NIGHT...WITH THE SFC
CAD LAYER EAST OF THE MOUNTAINS VERY SLOWLY WARMING. A 50 KT 850 MB
JET WILL ARRIVE IN THE SW FLOW BY 12Z ON MONDAY AND SLOWLY TRANSIT
THE REGION FROM THE WEST. AS THE COLD FRONT HELPS TO SCOUR THE WEDGE
OUT THROUGH THE DAY...THE WARM SECTOR WILL BE UNCOVERED OVER THE
LOWER PIEDMONT. THIS IS WHERE THE BEST COMBINATION OF DEEP SHEAR AND
INSTABILITY COULD POSE A SEVERE TSTM THREAT MON AFTN. WILL CONTINUE
LIKELY POPS THROUGHOUT...WITH TEMPS WARM ENOUGH TO SUPPORT ONLY RAIN
SHOWERS FROM SUN NIGHT THROUGH MONDAY...BUT WITH SCATTERED TSTMS
BECOMING INCREASINGLY LIKELY.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
AS OF 245 AM EST FRIDAY...THE LATEST 00Z GFS/ECMWF HAVE COME INTO
BETTER AGREEMENT ON A GENERAL SYNOPTIC PATTERN THROUGH THE MEDIUM
RANGE PERIOD.

OUR FORECAST AREA WILL BE UNDER PERSISTENT SWLY FLOW ALOFT MON NIGHT
INTO TUE. A DE-AMPLIFYING LONG WAVE UPPER TROUGH WILL THEN SWING
ACROSS THE EASTERN STATES TUE NIGHT...FOLLOWED BY ZONAL FLOW ALOFT
ACROSS THE REGION WED/THU.

AT THE SURFACE...BOTH THE 00Z GFS/ECMWF HAVE TRENDED A BIT SLOWER
WITH A COLD FRONT PUSHING THROUGH THE AREA ON TUESDAY. MODELS AGREE
THAT THE COLD FRONT WILL REMAIN STALLED IN THE VICINITY OF THE NC
MTNS THROUGH MON NIGHT BEFORE SLOWLY PUSHING SEWARD BY EARLY TUE
MORNING. THE FRONT WILL CONTINUE TO SLOWLY TRAVERSE THE REGION
THROUGH TUE AFTERNOON AND OFF TO THE EAST BY TUE EVENING. POPS HAVE
BEEN INCREASED A BIT FOR MOST LOCATIONS AT LEAST THROUGH MIDDAY ON
TUE TO ACCOUNT FOR THE LATEST MODEL TREND. WITH AN ARCTIC AIRMASS
SPILLING IN BEHIND THE FRONT...RAIN SHOWERS WILL CHANGE OVER TO SNOW
MON NIGHT MAINLY ALONG THE TN BORDER LINE. SEVERE WEATHER IS NOT
EXPECTED ON TUESDAY DUE TO NEAR ZERO INSTABILITY. PRECIP SHOULD
TAPER OFF TOWARD TUE EVENING AS THE FRONT PUSHES OFF TO THE EAST AND
A COLD CANADIAN HIGH PRESSURE BUILDS IN FROM THE NW. THE NEW 00Z
ECMWF HAS FOLLOWED THE DRY GFS SOLUTION WED/THU WITH THE HIGH
CENTERED JUST TO OUR NORTH BRINGING DRY CONDITIONS THRU THIS PERIOD.
TEMPERATURES WILL START OUT AROUND 3-5 DEGREES BELOW NORMAL ON
TUESDAY AND A GRADUAL DOWNWARD TREND EXPECTED THRU DAY 7.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...A BLEND OF MODEL GUIDANCE WOULD BRING CIGS TO VFR THIS
AFTERNOON AND LEAVE THEM THERE UNTIL LATE THIS EVENING...WHEN MVFR
RETURNS. BY DAYBREAK LIFR IS SUGGESTED....FOLLOWED BY A RETURN TO
MVFR AFTER DAYBREAK. GUIDANCE ONLY BRING THE VSBY DOWN TO MVFR JUST
BEFORE DAYBREAK AS WINDS STAY UP FROM THE SW AHEAD OF COLD FRONT.
FRONTAL PASSAGE WILL BE JUST AFTER DAWN...WITH WINDS VEERING TO
NW...AND THEN NE. RAIN CHANCES WILL BE BEST AROUND DAYBREAK...BUT
THUNDER CHANCES ARE TOO SMALL TO MENTION. LOW LEVEL WIND SHEAR IS
BRIEFLY SUPPORTED BY THE MODELS LATE THIS EVENING.

ELSEWHERE...GUIDANCE SUGGEST LOW VFR CIGS IN SC...AND MVFR IN NC
THIS AFTERNOON. SC SITES JOIN THE NC SITES WITH MVFR THIS EVENING.
TOWARD DAWN IFR IS SUPPORTED IN SC...AND LIFR IN NC. CIGS RISE TO
MVFR AFTER A COLD FRONT MOVES THROUGH EARLY SATURDAY. WITH WINDS
STAYING UP FROM THE SW AHEAD OF THE FRONT...GUIDANCE ONLY SUGGEST
MVFR VSBY TOWARD DAYBREAK. WINDS VEER NW BEHIND THE FRONT...THEN NE
EAST OF THE MOUNTAINS...EXCEPT AT KAND WHERE THEY REMAIN W. RAIN
CHANCES WILL BE HIGHEST IN THE MOUNTAINS AHEAD OF THE FRONT...THEN
ALONG THE FRONT AS IT CROSSES THE FOOTHILLS EARLY SATURDAY. THUNDER
CHANCES WILL BE BEST IN THE MOUNTAINS THIS AFTERNOON AND EARLY
EVENING...BUT NOT WORTH MENTIONING THEREAFTER. LOW LEVEL WIND SHEAR
IS BRIEFLY SUPPORTED AT SEVERAL SITES LATE THIS EVENING.

OUTLOOK...A MOIST AND ACTIVE PATTERN WILL CONTINUE ACROSS THE REGION
THRU EARLY NEXT WEEK. RESTRICTIVE CEILINGS EACH NIGHT AND PERHAPS
WELL THRU THE DAYLIGHT HOURS...ESPECIALLY ACROSS THE MTNS CAN BE
EXPECTED.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH 100%     HIGH  92%     MED   75%     HIGH  96%
KGSP       HIGH 100%     HIGH  92%     MED   72%     HIGH  89%
KAVL       HIGH  81%     HIGH  86%     HIGH  81%     HIGH  89%
KHKY       MED   66%     MED   75%     MED   76%     HIGH  90%
KGMU       HIGH  97%     HIGH  89%     MED   75%     HIGH  86%
KAND       HIGH 100%     HIGH  94%     MED   75%     HIGH  88%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE
HOURLY EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE
FORECASTS ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.CLIMATE...
RECORD HIGH TEMPERATURES FOR FRIDAY DEC 6TH...

AVL...73 IN 1998
CLT...78 IN 1998
GSP...76 IN 1998

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...WINTER STORM WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY
     EVENING FOR NCZ033-049-050-501>503-505.
SC...NONE.

&&

$$
SYNOPSIS...JOH
NEAR TERM...CDG/JAT
SHORT TERM...HG
LONG TERM...JOH
AVIATION...JAT
CLIMATE...