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000
FXUS62 KGSP 072018
AFDGSP

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

.SYNOPSIS...
CANADIAN HIGH PRESSURE WILL 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 FOR WEDNESDAY INTO FRIDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
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 NIGHT THROUGH TUESDAY/...
AS OF 315 PM SAT...CAD WILL STILL BE IN PLACE AT THE BEGINNING OF
THE PERIOD SUN NITE. HOWEVER...WEDGE WILL BECOME INCREASINGLY
PINCHED AS MILLER-B LOWS MOVE NORTH OF THE AREA ALONG THE COAST AND
TO OUR WEST. IN FACT...COLD SFC LAYER WILL BEGIN ERODING FROM THE
TOP DOWN AS STRONG H85 WAA DEVELOPS OVERNIGHT. THAT SAID...PRECIP
REMAINS LIQUID RAIN CONTINUE OVERNIGHT WITH A SLIGHT WARMING TREND
AROUND THE EDGES OF THE WEDGE.

THERE MAY BE SOME LINGERING COOL POOLING MON...BUT CAD SHUD CONTINUE
TO ERODE AS UPPER LEVEL CONFLUENCE ENDS AND COLD FRONT MOVES INTO
THE WRN CWFA. THE COLD FRONT ONLY SLOWLY MOVES EAST ACROSS THE AREA
MON AND MON NITE AS SFC WAVES MOVE NORTH ALONG THE FRONT. THIS COULD
LEAD TO PERIODS OF MODERATE RAIN ACROSS THE SWRN NC MTNS DURING THIS
PERIOD. RIGHT NOW...IT LOOKS LIKE ANY HEAVY RAIN WOULD BE FROM
DURATION...AND EVEN THEN...EXCESSIVE RAINFALL AMOUNTS APPEAR
UNLIKELY. HIGHS ACTUALLY WARM TO NEAR NORMAL OUTSIDE OF THE MTNS
MONDAY AND A LITTLE ABOVE OVER THE MTNS. LOWS MON NITE WARM TO 10 TO
15 DEGREES ABOVE NORMAL.

THE FRONT FINALLY MOVES EAST OF THE AREA TUE TAKING THE WIDESPREAD
PRECIP WITH IT. THERE MAY BE A SURGE OF INSTABILITY OVER THE ERN
UPSTATE AND SRN NC PIEDMONT DURING THE AFTERNOON LEADING TO ISOLATED
TSRA. HIGHS COOL TUE...WITH READINGS AS MUCH AS 5 DEGREES BELOW
NORMAL.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
AS OF 235 PM EST ON SATURDAY...THE MEDIUM RANGE MODELS ARE IN FAIR
AGREEMENT...GOOD ON SYSTEMS...BUT DIFFERENCES IN THE TIMING OF THOSE
SYSTEMS. GFS IS SLOW IN TAKING THE LAST OF THE PRECIP OUT OF THE
AREA...NOT UNTIL WEDNESDAY MORNING.  THIS IS DIFFERENT FROM PREVIOUS
RUNS AND THE ECMWF STILL HAS ALL REMAINING PRECIP MOVING SE OF AREA
AT 00Z WEDNESDAY.  GOING WITH THE ECMWF ON THIS AND DRYING OUR AREA
OUT TUESDAY EVENING AND TURNING COLDER WITH HIGH PRESSURE ADVECTING
THIS IN FROM NORTH.  LOOKS LIKE BEST PRESSURE GRADIENT FOR ANY
CONTRIBUTION TO WIND WEDNESDAY EVENING.  CENTER OF THE HIGH SHOULD
BE BETWEEN RALEIGH AND RICHMOND AROUND 12Z FRIDAY.

AS NEXT TROUGH DIGS SOUTH ACROSS THE PLAINS AND MISSISSIPPI VALLEY
ON FRIDAY...A SURFACE LOW SHOULD DEVELOP OVER THE NRN GULF AND MOVE
NE INTO THE WEEKEND. DRY AIR IN PLACE AHEAD OF THE LOW AND IN WAKE
OF THE DEPARTING HIGH MAY PRODUCE SOME BRIEF WINTRY PRECIP AS
EVAPORATIONAL COOLING TAKES PLACE THROUGH THE VERTICAL COLUMN.  THIS
SHOULD CHANGE OVER TO RAIN AS THE LOW TRACKS FROM THE NE GULF TO THE
CAROLINA COAST. AT THIS TIME...DOES NOT APPEAR THAT THERE WILL BE
ENOUGH COLD AIR ADVECTION TO PROVIDE A WINTRY CHANGE IN THE MTNS
THROUGH THE DAY SATURDAY. THERE WILL BE A COLD HIGH COMING DOWN
ACROSS THE GREAT LAKES...BUT TIMING WILL HAVE TO BE WATCHED. LOW
MOVES OFF CAROLINA COAST SATURDAY NIGHT AND AXIS OF DEEP 500MB
TROUGH DOES NOT CROSS BETWEEN 12Z AND 18Z SUNDAY.

TEMPERATURES WILL BE SEVERAL DEGREES BELOW NORMAL FROM WEDNESDAY
INTO NEXT WEEKEND.

&&

.AVIATION /20Z 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...

            20-02Z        02-08Z        08-14Z        14-20Z
KCLT       HIGH  81%     HIGH  85%     HIGH  93%     HIGH  88%
KGSP       HIGH  82%     HIGH  96%     HIGH  86%     HIGH  85%
KAVL       HIGH  92%     HIGH  99%     MED   68%     HIGH  87%
KHKY       MED   76%     HIGH  89%     HIGH  94%     HIGH  90%
KGMU       HIGH  82%     HIGH  95%     HIGH  92%     HIGH  82%
KAND       HIGH  92%     MED   76%     MED   79%     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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...ICE STORM WARNING FROM MIDNIGHT TONIGHT TO 8 PM EST SUNDAY FOR
     NCZ033-050-501-503-505.
     FREEZING RAIN ADVISORY FROM MIDNIGHT TONIGHT TO 8 PM EST
     SUNDAY FOR NCZ035>037-049-053-056-065-502-504-506-507-509.
SC...NONE.

&&

$$
SYNOPSIS...DEO
NEAR TERM...JAT
SHORT TERM...RWH
LONG TERM...DEO
AVIATION...JAT