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000
FXUS62 KGSP 071724
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1224 PM EST SAT DEC 7 2013

.SYNOPSIS...
A COLD FRONT WILL SLOWLY CROSS THE FORECAST AREA TODAY. CANADIAN
HIGH PRESSURE WILL THEN BUILD IN FROM THE NORTHEAST SUNDAY WITH
MOIST SOUTHERLY FLOW ALOFT MAINTAINED INTO MONDAY. ANOTHER COLD
FRONT IS EXPECTED TO CROSS THE AREA TUESDAY WITH RELATIVELY COLD
HIGH PRESSURE BUILDING BACK IN THROUGH THURSDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
1715 UTC UPDATE...SKY COVER AND POPS HAVE BEEN ADJUSTED PER
SATELLITE AND RADAR TRENDS. WINDS WERE UPDATED WITH A BLEND OF THE
LATEST ADJMAV AND NAM...WITH GUSTS ONLY DIMINISH SLIGHTLY OVERNIGHT.

AT 0930 EST SATURDAY...A POSITIVELY TILTED UPPER RIDGE EXTENDED FROM
THE BAHAMAS TO THE CENTRAL ATLANTIC...WHILE A SIMILARLY TILTED UPPER
TROUGH EXTENDED FROM EASTERN CANADA TO BAJA CALIFORNIA. A 130 KNOT
PLUS UPPER JET MAX WAS LOCATED FROM THE SOUTHERN GREAT LAKES TO NEW
ENGLAND. A CHANNELED VORT MAX WAS LOCATED OVER THE TN VALLEY AND
CENTRAL APPALACHIANS. A SLOW MOVING COLD FRONT WAS LOCATED FROM THE
NC OUTER BANKS...TO A WAVE IN THE CENTRAL SAVANNAH RIVER
VALLEY...THE THE FL PANHANDLE. PRECIPITATION ASSOCIATED WITH THIS
BOUNDARY WAS WELL EAST OF OUR AREA.

A STRONG SHORTWAVE WILL DIVE INTO THE BASE OF THE UPPER TROUGH IN
THE SW USA TODAY...RESULTING IN MINOR HEIGHT RISES OVER THE
SOUTHEAST USA. MOISTURE NORTH OF FRONT WILL LINGER OVER MUCH OF THE
THE PIEDMONT...HOWEVER SATELLITE IMAGERY SHOWS EXTENSIVE BREAKS OVER
THE FOOTHILLS AND MOUNTAINS. WITH LITTLE OR NO LIFT OVER AN ARRIVING
SURFACE RIDGE...ONLY SMALL POPS WILL BE CARRIED...WITH THE BEST
CHANCE IN THE PIEDMONT. COLD ADVECTION BEHIND THE STRONG COLD FRONT
WILL RESULT IN FALLING TEMPERATURES THROUGH THE DAY IN NORTHERN A
WESTERN SECTION OF THE AREA...AND OVER THE REST OF THE AREA BY
AFTERNOON. MAXIMUM TEMPERATURES WILL BE NEAR NORMAL ALONG AND SOUTH
OF INTERSTATE 85...BUT BELOW NORMAL TO THE NORTH.

BY THIS EVENING THE ABOVE MENTIONED SURFACE RIDGE WILL BE
SETTING UP ACROSS THE NORTHEAST AS A 1036MB HIGH YIELDS A DEEP
CLASSIC CAD WEDGE ACROSS THE SOUTHERN APPALACHIANS.  NORTHEASTERLY
FLOW AROUND THE WEDGE WILL PROMOTE COOLER TEMPERATURES ACROSS THE
NORTHERN NC PIEDMONT ALONG WITH THE MOUNTAINS/FOOTHILLS OF NC.
MEANWHILE...ISENTROPIC LIFT REGIME WILL RAMP UP LATE ON SATURDAY
EVENING INTO SUNDAY MORNING AS SURFACE LOW ACROSS THE SOUTHERN
PLAINS EJECTS TO THE NORTHEAST.  GUIDANCE HAS TRENDED BACK SLIGHTLY
WITH QPF DURING THE OVERNIGHT HOURS OF SUNDAY MORNING.  MODEL
SOUNDINGS ARE INDICATIVE OF SIGNIFICANT ICING ACROSS THE NORTHERN NC
MOUNTAINS ON SUNDAY MORNING.  WARM LAYER ALOFT DUE TO ISENTROPIC
UPGLIDE WITH PRECIPITATE INTO SHALLOW SUBFREEZING LAYER AT THE
SURFACE ALLOWING FOR RAIN TO FREEZE ON CONTACT.  DUE TO THE DEPTH OF
THE WARM LAYER ALOFT...NOT EXPECTING MIXED PTYPE WITH THIS SYSTEM.
MODEL QPF DECREASES FURTHER EAST AND WILL NOT WARRANT WARNING LEVEL
ICE ACCUMULATIONS.  AREAS SOUTH OF THE I40 CORRIDOR WILL SEE SURFACE
TEMPERATURES ABOVE FREEZING WITH THE EXCEPTION OF SOME OF THE HIGHER
PEAKS...THEREFORE NOT EXPECTING ANY SIGNIFICANT ACCUMULATING ICE IN
THESE ZONES.  THUS...WILL UPGRADE PORTIONS OF THE CURRENT WINTER
STORM WATCH ACROSS THE HIGHER TERRAIN TO AN ICE STORM WARNING
STARTING EARLY SUNDAY MORNING LASTING THROUGH SUNDAY AFTERNOON AS
ICE ACCUMULATIONS OF AT LEAST A QUARTER INCH ARE EXPECTED.  WILL
ALSO CANCEL WINTER STORM WATCH ACROSS THE NORTHERN TIER OF NC ZONES
EAST OF THE NEW ICE STORM WARNING AND ISSUE FREEZING RAIN ADVISORY
AS ACCUMULATIONS SHOULD BE LESS THAN A QUARTER INCH IN THESE AREAS.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
AS OF 230 AM EST SAT...THE WINTER WEATHER FORECAST FOR SUNDAY
REMAINS VERY CHALLENGING. THE 00Z MODEL RUNS TRENDED A BIT LOWER ON
QPF...BUT WITH PESKY SFC WET BULB TEMPS LIKELY TO LOCK IN VERY CLOSE
TO FREEZING N OF INTERSTATE 40. THE SYNOPTIC SETUP INCLUDES DEEP
LAYER SW FLOW REMAINING OVER THE AREA SUN THROUGH MON...AS WRN
ENERGY CONTINUES TO EVOLVE IN THE TROUGH AXIS LINGERING OVER THE
ROCKIES AND THE HIGH PLAINS. THE STRONGEST ISENTROPIC LIFT AHEAD OF
THIS SYSTEM WILL AFFECT WRN NC SUNDAY MORNING BEFORE THE STRONG 850
MB BAROCLINIC ZONE LIFTS NWD ACROSS VA THROUGH THE REST OF THE DAY.
LOW LEVEL AGEOSTROPHIC WIND ADJUSTMENTS SHOULD BE FULLY UNDERWAY
SUNDAY MORNING...WITH THE BEST POTENTIAL FOR SFC WET BULB TEMPS TO
LOCK IN AROUND FREEZING ALONG AND JUST EAST OF THE NRN BLUE RIDGE.
THUS...THE AREA FROM ERN AVERY/MITCHELL ACROSS WRN CALDWELL/BURKE
MCDOWELL IS THE ONLY AREA AT PRESENT WHERE CONFIDENCE ON DAMAGING
ICE ACCUMULATIONS WILL BE HIGH ENOUGH TO UPGRADE TO AN ICE STORM
WARNING. CONFIDENCE IS STILL 50/50 FOR THE REST OF CALDWELL
COUNTY...WITH GENERALLY A LIGHT ICING EVENT NOW FEATURED FOR THE
NEXT TIER OF COUNTIES FROM DAVIE THROUGH THE HKY AREA BACK TO
HENDERSON/BUNCOME/YANCEY. TEMPS SHOULD WARM ABOVE FREEZING
THROUGHOUT BY SUNDAY EVENING.

THE SFC CAD LAYER WILL GET INCREASINGLY PINCHED AGAINST THE HIGHER
TERRAIN SUN NIGHT AS ONE LOW PRESSURE CENTER MOVES UP THE ERN
SEABOARD AND ANOTHER SFC LOW MOVES INTO THE GREAT LAKES REGION. THE
DEEPEST MOISTURE PLUME E OF THE COLD FRONT TRAILING THE GREAT LAKES
LOW WILL REMAIN ALONG THE SRN APPALACHIANS SUN NIGHT THROUGH MON.
MECHANICAL FORCING IN THE SW UPSLOPE FLOW AHEAD OF THIS BOUNDARY
SHOULD CREATE A LOCAL RAINFALL MAXIMUM IN THE EXTREME SW MTNS. STILL
ANTICIPATE THAT RATES WILL BE TOO LOW TO WARRANT A FLOOD WATCH...BUT
WILL KEEP THE HEAVY RAIN AND ISOLATED FLOODING POTENTIAL MENTIONED
IN THE HWO SUN NIGHT AND MON FOR THE SW MTNS. CAD EROSION WILL BE
WEAK THROUGH MON...BUT WITH STEADY WARMING OF TEMPS. THERE COULD BE
SOME SFC BASED INSTABILITY UNCOVERED ALONG THE SE FRINGE MON
AFTN...BUT WITH CONFIDENCE TOO LOW TO MENTION ANY THUNDER.

THE WRN SYSTEM WILL FINALLY SHEAR EWD ON TUE...ALLOWING THE SURFACE
BOUNDARY TO GRADUALLY SLIP E ACROSS THE AREA. ANOTHER SURGE OF SFC
BASED INSTABILITY MAY AFFECT THE FAR SE PIEDMONT WHERE AN ISOLD
THUNDER MENTION WILL BE WARRANTED. THE TOP DOWN COOLING FROM THE W
WILL RACE THE EWD DEPARTURE OF THE MOISTURE...WITH SOME MTN SNOW
SHOWERS POSSIBLE NEAR THE TN LINE THROUGH THE DAY...BUT WITH LITTLE
TO NO ACCUM.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
AS OF 210 AM EST ON SATURDAY...MODELS ARE IN GOOD AGREEMENT THROUGH
THE MEDIUM RANGE PERIOD. NEARLY FLAT UPPER PATTERN WILL PERSIST
ACROSS THE SE TUE NIGHT INTO WED NIGHT. A LOW AMPLITUDE UPPER TROUGH
WILL THEN QUICKLY SWING ACROSS THE REGION ON THURSDAY...FOLLOWED BY
WEAK UPPER RIDGING ON FRIDAY.

AT THE SURFACE...PRECIP SHOULD TAPER OFF BY TUE NIGHT AS A COLD
FRONT PUSHES OFF THE ATLANTIC COAST AND A DRY CANADIAN HIGH PRESSURE
BUILDS IN FROM THE NORTH. THE HIGH WILL REMAIN ANCHORED TO OUR NORTH
WEDNESDAY THROUGH THURSDAY...BRINGING BELOW NORMAL TEMPS AND DRY
CONDITIONS TO MUCH OF THE REGION. THE HIGH WILL THEN GRADUALLY MOVE
INTO THE MID ATLANTIC STATES FRIDAY THROUGH EARLY SAT...WITH
INCREASING MOIST ISENTROPIC LIFT EXPECTED DURING THIS PERIOD.
HOWEVER...DRY CONDITIONS WILL PREVAIL AT LEAST THROUGH FRI AS MODELS
HAVE TRENDED SLOWER WITH THE ONSET OF ISENTROPIC INDUCED PRECIP.
HENCE...HAVE KEPT POPS BELOW 14 THROUGH FRI BEFORE RAMPING UP TO
SLIGHT CHANCE RANGE BY LATE FRI NIGHT. SURFACE TEMPS AND
THICKNESS ON FRI NIGHT MAY SUPPORT WINTRY PRECIP...MAINLY IN THE
MTNS AND NC FOOTHILLS AT THIS TIME. TEMPERATURES WILL RUN AROUND
5-10 DEGREES BELOW NORMAL THRU MUCH OF THE PERIOD.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT...THE MVFR CIG IS EXPECTED TO BRIEFLY LIFT OT LOW VFR THIS
AFTERNOON...THEN LOWER TO BACK TO MVFR THIS EVENING AND IFR BY
DAYBREAK SUNDAY. THE GUIDANCE CONSENSUS WOULD LEAVE THE CIG IFR FOR
MUCH OF SUNDAY MORNING. INCREASING MOIST LOW LEVEL LIFT WILL
INCREASE PRECIPITATION CHANCES OVERNIGHT...AND THE COMBINATION OF A
LOW DEW POINT DEPRESSION AND RAIN IS EXPECTED TO LOWER VSBY TO MVFR
TOWARD DAYBREAK...AND KEEP IT THERE INTO SUNDAY MORNING. ALTHOUGH
RAIN WILL FALL THOUGH A COLD LOWER LAYER...AT THIS POINT SURFACE
TEMPERATURES ARE EXPECTED TO BE WARM ENOUGH TO KEEP PRECIPITATION
ALL LIQUID. NE SURFACE WINDS WILL PERSIST.

ELSEWHERE... INTERMITTENT MVFR CIGS REMAIN POSSIBLE IN THE FOOTHILLS
THIS AFTERNOON...PERHAPS LIFTING BRIEFLY TO MVFR. MOIST LOW LEVEL
LIFT WILL SUPPORT MVFR CIGS AT ALL SITES THIS EVENING...AND LIFR BY
DAWN SUNDAY...WHICH PERSISTS INTO SUNDAY MORNING. RELATIVE HUMIDITY
AND INCREASING PRECIPITATION WILL SUPPORT MVFR VSBYS AT FOOTHILLS
SITES BY SUNDAY MORNING...AND IFR AT NC SITES. AT THIS POINT SURFACE
TEMPERATURES WILL SUPPORT LIQUID RAIN AT ALL FIELDS...ALTHOUGH KHKY
COULD BE MARGINAL. FOOTHILL WINDS WILL PERSIST OUT OF THE NE...BUT
WILL VEER SE AT KAVL BY DAWN.

OUTLOOK...RESTRICTIVE CIGS AND VSBY CAN BE EXPECTED IN PRECIPITATION
THROUGH MONDAY. A LIGHT GLAZE OF ICE IS POSSIBLE IN THE NRN NC
MTNS/FOOTHILLS SATURDAY NIGHT. STRONG THUNDERSTORMS ARE POSSIBLE
MONDAY ACROSS MAINLY UPSTATE SC. DRIER AIR RETURNS BY MID WEEK.

CONFIDENCE TABLE...

            17-23Z        23-05Z        05-11Z        11-17Z
KCLT       HIGH  89%     MED   77%     HIGH  90%     HIGH  91%
KGSP       MED   76%     HIGH  90%     HIGH  91%     HIGH  88%
KAVL       HIGH  95%     HIGH  91%     HIGH  91%     HIGH  81%
KHKY       HIGH  85%     HIGH  81%     HIGH  96%     HIGH  91%
KGMU       HIGH  82%     HIGH  84%     HIGH  91%     HIGH  88%
KAND       HIGH  91%     MED   77%     HIGH  94%     HIGH  83%

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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...ICE STORM WARNING FROM MIDNIGHT TONIGHT TO 8 PM EST SUNDAY FOR
     NCZ033-050-501-503-505.
     WINTER STORM WATCH FROM MIDNIGHT EST TONIGHT THROUGH SUNDAY
     EVENING FOR NCZ502.
     FREEZING RAIN ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EST
     SUNDAY FOR NCZ035>037-049-053-056-065-504-506-507-509.
SC...NONE.

&&

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