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000
FXUS62 KGSP 060545
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1245 AM EST FRI DEC 6 2013

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

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 1245 AM EST FRIDAY...NO SIGNIFICANT CHANGES NEEDED TO THE
FORECAST AT THIS TIME.  DID MAKE SLIGHT ADJUSTMENTS TO THE EXTREME
NEAR TERM TEMPERATURES...DEWPOINTS...AND POPS TO ACCOUNT FOR LATEST
OBS/RADAR TRENDS.  OTHERWISE KEPT FORECAST AS IS FOR THIS UPDATE.

PREVIOUS DISCUSSION...

AT 230 PM EST THURSDAY...A POSITIVELY TILTED UPPER
RIDGE WILL SLOWLY PUSH OFF THE EAST COAST TONIGHT AND FRIDAY...WHILE
A BROAD AND POSITIVELY TILTED UPPER TROUGH ADVANCES ACROSS CENTRAL
CANADA AND THE WESTERN HALF OF THE USA. THE TROUGH REMAINS
SUFFICIENTLY WEST OF THE APPALACHIANS TO KEEP SHORTWAVE ENERGY OVER
THE TN VALLEY.

WEAKENING ISENTROPIC UPGLIDE OVER DEPARTING HIGH PRESSURE WILL LOWER
PRECIPITATION CHANCES OVER THE PIEDMONT TONIGHT...WHILE INCREASING
SW LOW LEVEL FLOW PRODUCES A MARGINAL SW UPSLOPE FLOW COMPONENT INTO
THE SOUTHERN MOUNTAINS. THE GREATEST PRECIPITATION IS EXPECTED TO
FOCUS ALONG THE SOUTH FACING BLUE RIDGE...BUT AMOUNTS ARE NOT
EXPECTED TO BE EXCESSIVE. MODEST ELEVATED INSTABILITY WILL BE
PRESENT IN THE UPPER SAVANNAH RIVER VALLEY AND OVER THE
MOUNTAINS...BUT THE BETTER SHEAR WILL BE BENEATH THE UNSTABLE
LAYER...AND ORGANIZED CONVECTION IS NOT EXPECTED AT THIS TIME.

THE COLD FRONT WILL VERY SLOWLY MOVE INTO THE MOUNTAINS ON
FRIDAY...PROVIDING A FOCUS FOR PRECIPITATION...WHILE THE MODELS
SUGGEST A DECREASE IN MOISTURE OVER THE PIEDMONT IN THE WARM SECTOR.
VERY LIMITED ELEVATED INSTABILITY IS EXPECTED TO SPREAD INTO THE
FOOTHILLS AND PIEDMONT ON FRIDAY...AGAIN ABOVE THE BEST LOW LEVEL
SHEAR. AT THIS POINT NOTHING MORE THAN ISOLATED THUNDERSTORMS ARE
EXPECTED.

MINIMUM TEMPERATURES TONIGHT WILL RUN MORE THAN 20 DEGREES ABOVE
NORMAL TONIGHT IN WARM ADVECTION UNDER CLOUD COVER...WITH HEIGHTS
STILL ABOVE NORMAL. MAXIMUMS TEMPERATURE ON FRIDAY WILL RUN 15 OR
MORE DEGREES ABOVE NORMAL AS WARM ADVECTION OFFSETS FALLING HEIGHTS
ALOFT AND CLOUD COVER.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
AS OF 230 PM EST THURSDAY...A COLD FRONT WILL MOVE INTO THE NC MTNS
FRIDAY EVENING. THE FRONT REPRESENTS THE LEADING EDGE OF AN ARCTIC
AIRMASS. AS IS TYPICAL WITH THIS TYPE OF AIRMASS IT WILL HAVE
TROUBLE MAKING IT ACROSS THE MOUNTAINS...THOUGH BY 12 UTC SATURDAY
IT SHOULD HAVE MOVED THROUGH MOST OF THE FORECAST AREA. THERE WILL
BE A NARROW RIBBON OF 300-500 J/KG CAPE VALUES ALONG THE
BNDRY...OVER THE SRN NC MTNS...FRIDAY EVENING. THE 0-3KM SHEAR
MAGNITUDE IS ON THE ORDER OF 40-50 KTS. WHILE THE RICHER BNDRY LAYER
AIR IS EXPECTED TO STAY A LITTLE TO THE SOUTH OF THE FORECAST
AREA...THESE PARAMETERS ARE SUFFICIENT TO SUPPORT A SMALL CHANCE OF
DAMAGING WINDS WITH ANY CONVECTION THAT MOVES INTO THE NC MTNS FRI
EVENING. FORTUNATELY...THE DEEP LAYER FORCING DOES NOT LOOK TO
SUPPORT ORGANIZED MCS ACTIVITY.

THE BAND OF PCPN ALONG THE FRONT BREAKS UP AND LARGELY GOES AWAY
LATE FRIDAY NIGHT AND SATURDAY. I/VE CUT BACK POPS INTO THE CHANCE
RANGE OVER MOST OF THE FA DURING THIS TIME...AND THAT MIGHT NOT BE
LOW ENOUGH. I/M CARRYING MAINLY CLOUDY SKIES ON SATURDAY...BUT THERE
IS A CHANCE THAT THE NRN ZONES WILL CLEAR UP FOR A WHILE IN THE
MORNING.

SATURDAY NIGHT AND SUNDAY ISENTROPIC UPGLIDE WILL DEVELOP OVER THE
WEDGE-RIDGE. THE 850-700 MB THICKNESSES ARE VERY WARM...THOUGH THE
1000-850 THICKNESS WILL BE LOW ENOUGH TO SUPPORT FREEZING RAIN OVER
PARTS OF THE NC BLUE RIDGE AND FOOTHILLS. THE SREF PLUME DIAGRAMS
SHOW OVER A HALF INCH OF FREEZING RAIN AT BOONE AND ABOUT 2 TENTHS
OF INCH OF ICE AT HICKORY. AS IS TYPICAL...THE GFS IS A LITTLE
WARMER. IT/S ALSO A LITTLE DRIER. IN FACT...THE AMOUNT OF PCPN THAT
THE GFS HAS OVER THE WEDGE WOULDN/T BE SUFFICIENT FOR DAMAGING ICE
ACCUMULATIONS WHILE THE NAM AND CANADIAN HAVE CLOSER TO A HALF INCH
OF LIQUID PCPN. THE ECMWF JUST CAME IN AND IT SUPPORTS THE LOWER
VALUES OF THE GFS. I/VE INCREASED THE AMOUNT OF FREEZING RAIN
CONSIDERABLY ALONG THE NC BLUE RIDGE...THE WRN FOOTHILLS AND THE
UPPER FRENCH BROAD VALLEY LATE SAT NIGHT AND SUNDAY MORNING. WE ARE
STILL DEALING WITH A LATE 5TH PERIOD AND 6TH PERIOD EVENT AND IT/S
WAY TOO EARLY TO ISSUE WATCHES. ALSO...THE UNUSUALLY WARM MID LEVEL
THICKNESSES AND THE GLOBAL MODEL/S RECENT TREND TOWARD LOWER QPF ADD
TO THE FORECAST UNCERTAINTY. HOWEVER...THE OVERALL TREND LOOKS TO
SUPPORT SOME AMOUNT OF FREEZING RAIN OVER OUR NRN ZONES EARLY
SUNDAY. AND IF THE HEAVIER QPF WERE TO VERIFY WE COULD EVEN SEE
DAMAGING ACCUMULATIONS OF ICE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 225 PM THURSDAY...PRETTY GOOD GUIDANCE AGREEMENT THRU THE
MEDIUM RANGE. AT LEAST UNTIL THE END OF THE PERIOD. SWLY FLOW STARTS
OUT OVER THE AREA AT THE BEGINNING OF THE PERIOD. SOME SHORT WAVE
ENERGY MOVES THRU THE FLOW AND OVER THE AREA THRU MON NITE. THE
ECMWF SWINGS A TROF ACROSS THE AREA TUE WITH NEARLY ZONAL FLOW
SETTING UP FOR WED. IN THEN BRINGS A DEVELOPING SRN STREAM UPPER LOW
TOWARD THE AREA THU. THE GFS BRINGS THE UPPER TROF TOWARD THE AREA
TUE...SHEARS IT OUT OVER THE AREA WED...THEN BLOWS A DAMPENED UPPER
TROF ACROSS THE AREA THU. AT THE SFC...THE WET WX CONTINUES FOR THE
EARLY PERIODS. THE CAD OVER THE AREA ERODES SUN NITE AS THE MILLER B
LOWS MOVE WELL NORTH OF THE AREA. STILL LOOKS LIKE A COLD...RAW AND
RAINY NITE WITH LIQUID RAIN THE ONLY P-TYPE. THE PRECIP CONTINUES
OVER THE AREA MONDAY AS A COLD FRONT SLIDES INTO THE AREA. THERE MAY
BE ENUF INSTABILITY FOR A T-STORM OR TWO OVER THE UPSTATE AND NE GA.
THE PRECIP LINGERS MON NITE AS THE FRONT ONLY SLOWLY SLIDES EWD...
THEN FINALLY ENDS FROM WEST TO EAST OVER THE AREA TUE AS DRY HIGH
PRESSURE BUILDS IN BEHIND THE SLOWLY MOVING FRONT. THERE COULD BE
ENUF COLD AIR BEHIND THIS SYSTEM FOR A MIX OR CHANGEOVER TO SNOW IN
THE HIGH ELEVATIONS OF THE NC MTNS. VERY LIGHT ACCUMS WOULD BE
POSSIBLE. THE FRONT THEN STALLS NEAR THE COAST AS WAVES OF LOW
PRESSURE MOVE ALONG THE FRONT. THE GFS KEEPS THE PRECIP EAST OF OUR
CWFA WHILE THE ECMWF BRINGS PRECIP BACK INTO THE AREA WITH A MILLER
A TYPE LOW AND ANOTHER CAD DEVELOPING. HAVE KEPT THE FCST DRY FOR
NOW GIVEN THE UNCERTAINTY.

LOWS SUN NITE SHOULD BE EARLY IN THE EVENING AS STRONG WAA TAKES
PLACE OVERNIGHT WITH HIGHS MONDAY AROUND 5 DEGREES ABOVE NORMAL.
LOWS MON NITE WILL BE COOLER OVER THE NC MTNS BUT WARMER ELSEWHERE.
A COOL DOWN BEGINS TUE WITH TEMPS FALLING BELOW NORMAL AND COOLING
EACH PERIOD.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
AT KCLT...MVFR TO LIFR CONDITIONS WILL PREVAIL THROUGH THE OVERNIGHT
HOURS AS WEAK ISENTROPIC UPGLIDE CONTINUES TO SATURATE THE LOW
LEVELS.  WILL INITIALIZE CIGS AT MVFR LEVELS WITH A TEMPO FOR SHRA
AND IFR CIGS AS SCATTERED SHOWERS CONTINUE TO MOVE ALONG THE I85
CORRIDOR.  CIGS WILL LIKELY DETERIORATE FURTHER AROUND THE 8Z
TIMEFRAME WERE LIFR CIGS REMAIN FROM PREVIOUS TAF ISSUANCE DUE TO
MODEL RUN CONSISTENCY.  SOUTH TO SOUTHWEST WINDS WILL REMAIN
ELEVATED WITH GUSTS APPROACHING 20KTS...WHICH WILL HELP TO KEEP VISB
RESTRICTIONS LIMITED OVERNIGHT.  EXPECTING THESE GUSTY WINDS TO
CONTINUE THROUGH THE REMAINDER OF THE TAF CYCLE.  OTHERWISE...CIGS
WILL IMPROVE TO MVFR LEVELS BY MID MORNING WITH VFR LEVELS RETURNING
BY EARLY AFTERNOON AS ISENTROPIC ASCENT WEAKENS DUE TO WESTERLY
VEERING FLOW.  FINALLY...AS A COLD FRONT APPROACHES FROM THE
WEST...DEEP LAYER MOISTURE OUT AHEAD WILL SPREAD ACROSS THE PIEDMONT
LATE IN THE PERIOD ONCE AGAIN LOWERING CIGS BACK TO MVFR LEVELS.

ELSEWHERE...ISENTROPIC ASCENT AHEAD OF APPROACHING COLD FRONT WILL
KEEP ALL SITES LOCKED IN WITH MVFR TO IFR RESTRICTIONS...WITH A FEW
HOURS OF LIFR POSSIBLE AT THE SC SITES AND KHKY.  SOUTH TO SOUTHWEST
WINDS WILL REMAIN GUSTY AT ALL SITES OVERNIGHT...EXCEPT FOR KAVL
WHERE VISB RESTRICTIONS COULD IMPEDE AIRFIELD BY MID MORNING DUE TO
WEAKER FLOW AT THE SURFACE.  THEREFORE ADDED IFR GROUPS FOR PATCHY
FOG AT KAVL.  AS THE SLOW MOVING COLD FRONT APPROACHES FROM THE WEST
LATE FRIDAY MORNING...INTRODUCED MENTION OF RA AT KAVL WHILE
KEEPING THE REMAINDER OF THE SITES DRY THROUGH THIS FORECAST CYCLE.

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...

            05-11Z        11-17Z        17-23Z        23-05Z
KCLT       MED   74%     MED   64%     HIGH  90%     MED   77%
KGSP       HIGH  90%     MED   79%     HIGH  95%     HIGH  82%
KAVL       HIGH  83%     HIGH  82%     MED   72%     MED   70%
KHKY       HIGH  87%     HIGH  86%     HIGH  90%     HIGH  80%
KGMU       HIGH  86%     HIGH  86%     HIGH  95%     HIGH  84%
KAND       LOW   54%     HIGH  81%     HIGH  84%     MED   75%

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...NONE.
SC...NONE.

&&

$$
SYNOPSIS...SBK
NEAR TERM...CDG/JAT/WIMBERLEY
SHORT TERM...MCAVOY
LONG TERM...RWH
AVIATION...CDG
CLIMATE...