000
FXUS62 KGSP 080244
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
944 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/...
900 PM UPDATE...SHORT TERM GUIDANCE CONTINUES TO SHOW LITTLE
RESPONSE TO WEAK UPGLIDE ALREADY OCCURRING OVER DEVELOPING WEDGE.
THIS UPGLIDE IS SHOWN BY 00Z NAM TO STRENGTHEN AFTER MIDNIGHT...AND
CORRESPONDINGLY THE MESO MODELS BRING SOME PRECIP IN THEN. HOURLY
QPF FROM THE CONSENSUS OF THESE MODELS MAXIMIZES AFTER DAYBREAK WITH
MOST AREAS SEEING A COUPLE HUNDREDTHS PER HOUR OF LIQUID. CAREFULLY
REVISITED TEMPS OVERNIGHT...OPTING NOT TO USE MIN TEMP
GUIDANCE...BUT RATHER TO GO HOUR BY HOUR. WITH PRECIP BEING
DELAYED...EVAPORATIONAL COOLING WILL BE DELAYED ALSO...POTENTIALLY
LIMITING HOW COLD TEMPS COULD DROP EARLY SUNDAY MORNING. NONETHELESS
HOURLY TEMPS FROM THE SHORT TERM GUIDANCE...LAMP...RAP AND LOCAL
WRF...INDICATE ENOUGH COOLING TO MAINTAIN FZRA FCST...THOUGH THIS
MAY BE MORE DUE TO CAA THAN WET BULB EFFECT. SOUNDINGS STILL SUPPORT
ALL FZRA DUE TO STRONG WARM NOSE DESPITE ANY ICE NUCLEATION ABOVE.
FZRA AREA EXPANDED SLIGHTLY PRIMARILY DUE TO REVISED QPF WHICH WAS
SLIGHTLY HIGHER AND ALSO SLIGHTLY MORE FOCUSED AROUND DAYBREAK WHEN
THE FORCING LOOKED BEST. HAYWOOD AND TRANSYLVANIA COUNTIES INCLUDED
ENOUGH AREA OF APPRECIABLE ICE ACCUMS TO ADD THEM TO THE FZRA
ADVISORY. NEW WSW PRODUCT JUST ISSUED. THOUGH PRECIP MAY NOT START
UNTIL AFTER 05Z WHEN HEADLINES TAKE EFFECT...TO MINIMIZE CONFUSION I
JUST LEFT START TIME AS-IS.

PREVIOUS DISCUSSION...
TONIGHT AND SUNDAY...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 /03Z SUNDAY THROUGH THURSDAY/...
AT KCLT...MESOSCALE MODELS SUGGEST UPGLIDE OVER DEVELOPING COLD
WEDGE IS UNLIKELY TO PRODUCE PRECIP UNTIL AFTER MIDNIGHT TONIGHT.
RESTRICTIVE CIGS SHOULD ARRIVE WITH THE PRECIP AND LAST THRU THE
REST OF THE PERIOD. MVFR CLOUDS MAY BE SEEN THIS EVENING BUT CIG
WILL REMAIN LOW VFR. MVFR VSBY EXPECTED FROM AROUND DAYBREAK ONWARD
WITH FOG AND RAIN. RAIN EXPECTED TO BE HEAVIEST IN 12-18Z TIMEFRAME.
GUIDANCE VARIES BETWEEN LIFR AND MVFR WRT DAYTIME CIGS SUNDAY...BUT
ALL SUGGEST VIRTUALLY NO IMPROVEMENT DURING THE DAY. WITH RAIN AND
CAD CONTINUING THAT SEEMS REASONABLE...SO IFR THRU 00Z. WINDS REMAIN
NE WITHIN WEDGE. SFC TEMPS AND DEEP WARM LAYER ALOFT SUPPORT AN ALL
LIQUID EVENT.

ELSEWHERE...PRECIP CHANCES INCREASE LATE TONIGHT GENERALLY FROM S TO
N AS WARM UPGLIDE INCREASES OVER COLD WEDGE IN CAD REGIME. VSBY
SHOULD BE VFR AND CIGS LOW VFR OR MVFR BEFORE PRECIP SETS IN...WHICH
WILL EVENTUALLY LOWER CIGS TO IFR /LIFR AT KAVL/ AND VSBY TO MVFR.
WITH VERY WARM AND DEEP WARM LAYER OVER THE COLD AIR AT THE
SFC...LOCATIONS WITH SUBFREEZING TEMPS THIS PERIOD WILL SEE FZRA.
THIS IS MAINLY AT HIGHER ELEVATIONS. KAVL AND KHKY CURRENTLY ARE
FCST TO STAY ABOVE 0C...SO NO MENTION MADE IN TAFS THEREOF...BUT IT
IS A CLOSE CALL WITH FZRA AND A LIGHT GLAZING POSSIBLE NEARBY BOTH.
RAIN MAY LOSE SOME INTENSITY OR BECOME LESS WIDESPREAD BY MIDDAY
SUN...BUT WITH THE WEDGE IN PLACE LITTLE TO NO IMPROVEMENT EXPECTED
THRU THE END OF THE PERIOD.

OUTLOOK...RESTRICTIVE CIGS AND VSBY CAN BE EXPECTED IN PRECIPITATION
THROUGH TUESDAY...ESPECIALLY EARLY EACH MORNING. DRIER AIR AND
FLIGHT CONDITIONS SHOULD RETURN MID-WEEK.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       HIGH  80%     MED   73%     HIGH  83%     HIGH  88%
KGSP       HIGH  89%     MED   73%     HIGH  83%     HIGH  88%
KAVL       HIGH  93%     MED   64%     MED   79%     MED   78%
KHKY       HIGH  85%     HIGH  91%     HIGH  83%     HIGH  88%
KGMU       HIGH  90%     MED   67%     HIGH  83%     HIGH  88%
KAND       HIGH  96%     MED   77%     HIGH  82%     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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...ICE STORM WARNING UNTIL 8 PM EST SUNDAY FOR NCZ033-050-501-503-
     505.
     FREEZING RAIN ADVISORY UNTIL 8 PM EST SUNDAY FOR NCZ035>037-
     049-052-053-056-064-065-502-504-506-507-509.
SC...NONE.

&&

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