000
FXUS62 KGSP 050246
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
946 PM EST WED DEC 4 2013

.SYNOPSIS...
MOIST SOUTHWESTERLY FLOW OFF THE GULF OF MEXICO WILL PERSIST ACROSS
THE REGION THROUGH THURSDAY. A COLD FRONT WILL THEN SLOWLY CROSS THE
FORECAST AREA FRIDAY AND FRIDAY NIGHT. CANADIAN HIGH PRESSURE
BUILDING IN FROM THE NORTHEAST OVER THE WEEKEND WITH MOIST SOUTHERLY
FLOW ALOFT.

&&

.NEAR TERM /THROUGH THURSDAY/...
930 PM UPDATE...SMALL AREA OF SHOWERS MOVING UP THRU CENTRAL GA. ON
ITS CURRENT TRACK IT IS SET TO REACH THE SW PORTIONS OF THE CWFA BY
11 PM. THIS IS ASSOCIATED WITH AN AREA OF SLIGHTLY BETTER MIDLEVEL
MOISTURE ADVECTION. 00Z NAM STILL SHOWS ISENTROPIC UPGLIDE BEST OVER
THE SW MTNS TONIGHT THOUGH IT IMPROVES TOWARD DAYBREAK ACRS THE
PIEDMONT. SFC BASED MOIST LAYER DEEPENS ALONG THE BLUE RIDGE AS
WELL. THUS POPS WERE REVISED TO FOCUS ON THE SRN FACING ESCARPMENT
EARLY ON THEN SPREAD ALONG THE BLUE RIDGE AND INTO THE PIEDMONT
NEARER DAYBREAK. THIS IS SIMILAR TO PREVIOUS TREND.

WRT DENSE FOG...HAVE YET TO SEE ANY OB SITES LOCK IN AT 1/4SM...WITH
MANY SITES ACRS THE AREA HAVING GONE DOWN TO 1/4 OR 1/2SM ONLY TO GO
BACK UP AND THEN DROP AGAIN. THIS SUGGESTS THE DENSE FOG IS STILL
QUITE PATCHY. SPS WAS ISSUED TO DISCUSS THAT A COUPLE HOURS AGO AND
UNLESS A CONTIGUOUS AREA LOCKS IN OVER THE NEXT HOUR...WILL JUST
REVISE THE SPS BEFORE IT EXPIRES AT 11 PM. AT ANY RATE FOG SHOULD BE
MORE OF A CONCERN AS THE NIGHT GOES ON...WITH MSTR ADVECTION
CONTINUING AND SLIGHT COOLING OCCURS AT THE SFC.

REVISED OVERNIGHT TEMPS PER 9 PM OBS...WITH LOWS BASICALLY A DEGREE
OR TWO BELOW CURRENT READINGS.

AS OF 220 PM...NEAR TERM MODELS INDICATE THAT A LOW PRESSURE SYSTEM
WILL CONTINUE TO ORGANIZE ACROSS THE GREAT LAKES REGION TONIGHT.
BROAD HIGH PRESSURE WILL REMAIN CENTERED OVER THE WESTERN ATLANTIC
TONIGHT. AS A COLD FRONT PUSHES ACROSS THE MID MISSISSIPPI RIVER
VALLEY...RETURN FLOW WILL INCREASE ACROSS THE FORECAST AREA. RECENT
SATELLITE LOOP INDICATES WIDESPREAD STRATUS ACROSS NE GA AND THE
FOOTHILLS AND PIEDMONT OF THE CAROLINAS...SLOWLY ERODING ACROSS NE
GA. IN ADDITION...BATCHES OF LOW CLOUDS WAS SLIDING NORTH ACROSS THE
DEEP SOUTH FROM THE GULF OF MEXICO. BASED ON THE SATELLITE TRENDS
AND LATEST MODEL RUNS...LLVL MOISTURE SHOULD INCREASE ACROSS THE CWA
DURING THE EVENING...WITH A SECONDARY INCREASE DURING THE PRE DAWN
HOURS. FORECAST SOUNDINGS INDICATE THAT CLOUD BASES WILL STEADILY
LOWER ACROSS THE CWA FROM MID EVENING ON. IN FACT...SOUNDINGS
INDICATE THAT A LLVL INVERSION WILL DEVELOP UNDER SLOW WAA. THE BL
BECOMES SATURATED ON MOST AREA SOUNDING BETWEEN 6-13Z...WITH
CONDENSATION PRESSURE DEFICITS LOWERING TO 0 TO 2-3 MBS BY 12Z. IT
APPEARS THAT MORNING CONDITIONS WILL FEATURE AREAS OF FOG...WITH VIS
RANGING FROM .25 TO 1 MILE. LOW TEMPERATURES TONIGHT WILL BE
COMPARABLE TO NORMAL HIGHS FOR THIS DATE. USING A BLEND OF
MOS...LOWS ARE FORECAST TO RANGE FROM 50 ACROSS THE MTNS VALLEYS TO
U50S EAST.

MTN AND FOOTHILL RAINFALL MAY GRADUALLY INCREASE IN COVERAGE THROUGH
TONIGHT. THE RAIN WILL BE PRIMARILY SUPPORTED BY UPSLOPE
FLOW...POSSIBLY AUGMENTED BY A FEW ROUNDS OF INCREASED ISENTROPIC
LIFT. DURING THE LATE NIGHT HOURS...ISENTROPIC LIFT MAY INCREASE
ACROSS THE PIEDMONT. I WILL INDICATE AN INCREASING AREA OF CHC
POPS...BEGINNING OVER THE MTNS THEN SPREADING ACROSS THE
MTNS...FOOTHILLS...AND PIEDMONT WEST OF I-77. RAINFALL AMOUNTS
TONIGHT MAY RANGE FROM 0.25 ACROSS THE UPSLOPE AREAS TO .05 EAST.

THURSDAY...THE COLD FRONT WILL PUSH EAST ACROSS THE OHIO RIVER
VALLEY...REACHING EAST TN BY 0Z FRI. NAM INDICATES THAT A BROAD
FIELD OF WEAK CAPE WILL DEVELOP ACROSS THE REGION DURING THE
AFTERNOON. LINGERING SHALLOW ISENTROPIC LIFT....UPSLOPE FLOW...AND
LIMITED INSTABILITY SHOULD SUPPORT NUMEROUS MTN SHRA TO SCT SHRA
ACROSS THE FOOTHILLS AND PIEDMONT. IN FACT...IT IS POSSIBLE ONE OR
TWO TSRA COULD DEVELOP DURING THE AFTERNOON. QPF...AN ADDITIONAL
0.25 IS EXPECTED ACROSS THE UPSLOPE AREAS TO .05 EAST. TEMPERATURES
SHOULD FAVOR VALUES NEAR 70.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 210 PM WEDNESDAY...GUIDANCE IN PRETTY GOOD AGREEMENT THRU THE
SHORT RANGE. THE CWFA REMAINS IN SWLY FLOW ALOFT THRU THE PERIOD
BETWEEN AN ANTICYCLONE CENTERED NEAR SRN FL AND AN UPPER LOW MOVING
THRU ERN CANADA. AT THE SFC...A COLD FRONT MOVES INTO THE
APPALACHIANS THU NITE AND REMAINS NEARLY STEADY FRI AS A SFC WAVE
MOVES NORTH ALONG THE FRONT. THE FRONT THEN CROSSES THE AREA FRI
NITE.

THIS PATTERN SETS UP A TIGHT MOISTURE AND PRECIP GRADIENT ACROSS THE
CWFA THU NITE AND FRI WITH DEEPER MOISTURE AND BETTER FORCING OVER
THE WEST AND GOOD LOW LEVEL MOISTURE AND LITTLE FORCING EAST. THAT
SAID...THE BEST MOISTURE AND SYNOPTIC SCALE FORCING REMAINS WEST OF
THE CWFA THU NITE AND FRI. THIS PUTS THE HIGHEST POP AND QPF NEAR
THE TN BORDER AND THE SWRN ESCARPMENT. WITH THE FRONT OVER THE WRN
CWFA THU NITE AND FRI...WEAK INSTABILITY WILL DEVELOP ACROSS THE WRN
CWFA WITH ISOLATED TO SCT TSRA FROM TIME TO TIME. TEMPS WILL ALSO BE
WELL ABOVE NORMAL. SLIGHT TO LOW END CHC POP WILL CONTINUE ACROSS
THE MIDDLE AND ERN CWFA IN THE WEAK FORCING AND GOOD LOW LEVEL
MOISTURE. PRECIP SPREADS ACROSS THE AREA WITH THE FRONT FRI NITE.
BEST POP WILL BE ACROSS NC WHERE BEST FORCING DEVELOPS...BUT LIKELY
POP DOES DEVELOP LATE IN THE NIGHT SOUTH OF I-85. EVEN THEN...STRONG
FORCING IS LIMITED SO BEST QPF WILL BE NEAR THE TN BORDER. LOWS FRI
NITE NOT AS WARM AS THU NITE...BUT STILL 10 TO AS MUCH AS 20 DEGREES
ABOVE NORMAL. BREEZY CONDITIONS WILL CONTINUE THRU THE PERIOD AS
WELL.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
AS OF 150 PM WEDNESDAY...SATURDAY WILL SEE A TRANSITION TO A CAD
REGIME...AS BACKDOOR COLD FRONT DROPS SOUTH ACROSS THE CWA THROUGH
THE DAY. THIS SHOULD RESULT IN MAXES OCCURRING AROUND 12Z...WITH
GRADUALLY FALLING TEMPS EXPECTED IN MOST AREAS. HOWEVER...IT WILL BE
INTERESTING TO SEE IF THE I-40 CORRIDOR CLEARS OUT DURING THE
AFTERNOON...AS SUGGESTED BY THE NAM/S DEPICTION OF DRIER AIR PUSHING
INTO THE AREA ON LOW LEVEL NE FLOW. IF SO...THE FALLING/STEADY TEMP
TREND WOULD BE REVERSED...AND WE WOULD LIKELY SEE NORTHERN AREAS
BEING THE WARM SPOT IN THE CWA DURING THE AFTERNOON. OTHERWISE... WE
SHOULD SEE DIMINISHING PRECIP CHANCES THROUGHOUT THE MORNING AND
EARLY/MID AFTERNOON...ESPECIALLY ACROSS NORTHERN AND WESTERN
AREAS...WHERE AT LEAST SOME DEEP LAYER DRYING IS ANTICIPATED...AND
FORCING WILL WEAKEN IN DIMINISHING ISENTROPIC UPGLIDE.

BY LATE AFTERNOON/EVENING SATURDAY...ISENTROPIC LIFT WILL ONCE AGAIN
INCREASE FROM SOUTH TO NORTH AS AN AREA OF HEIGHT FALLS OVERSPREADS
THE MISS VALLEY/SOUTHERN PLAINS...INDUCING CYCLOGENESIS OVER THE
LOWER MISS VALLEY/WESTERN GULF. LIKELY POPS WILL THEREFORE RETURN
FOR SAT NIGHT. AS CAD MATURES...FREEZING TEMPS COULD DEVELOP ALONG
THE EASTERN BLUE RIDGE ESCARPMENT BY SUNDAY MORNING. THE ECMWF AND
GFS HAVE CONTINUED THE TREND OF GRADUALLY WARMING THE LOWER
TROPOSPHERE WITH EACH SUCCESSIVE RUN. HOWEVER...EVEN FORECAST
SOUNDINGS FROM THE WARM GFS INDICATE A BRIEF PERIOD OF FZRA ACROSS
THE NORTHERN MTNS SUNDAY MORNING. CONFIDENCE IS STILL QUITE LOW...
AND WILL BE UNTIL THE NAM WINDOW...WITH ITS HIGHER RESOLUTION/
IMPROVED DEPICTION OF CAD...MOVES INTO THE SAT NIGHT/SUNDAY TIME
FRAME. AS SUCH...THE CURRENT HWO MENTION OF WINTRY PRECIP ALONG OUR
NORTHERN BLUE RIDGE AREAS STILL APPEARS WELL-PLACED.

THE SURFACE LOW LIFTS WEST OF THE APPALACHIANS LATE SUNDAY/SUNDAY
NIGHT...WHILE THE CAD PARENT HIGH MIGRATES INTO SOUTHEAST CANADA.
THIS IS A CLASSIC SETUP FOR CAD EROSION (NORTHWESTERN LOW W/ COLD
FRONT SCENARIO PER 2006 CSTAR STUDY)...LIKELY RESULTING IN WARMING
TEMPS THROUGHOUT SUNDAY NIGHT. IN FACT...BY 12Z SUNDAY...AT LEAST
OUR SOUTHERN AREAS WILL LIKELY BE IN THE WARM SECTOR. THIS IS
SIGNIFICANT...AS THE LATEST GFS DEPICTS A TONGUE OF LOW CAPE AHEAD
OF THE ADVANCING COLD FRONT. THIS IS ALIGNED WITH ABOUT 40 KTS OF
LOW LEVEL SHEAR. A GFS PROG THE SHERB PARAMETER (A HIGH SHEAR/LOW
CAPE SEVERE CONVECTIVE PARAMETER ORIGINATING FROM A RECENTLY
COMPLETED CSTAR PROJECT) EXCEEDS THE OPTIMAL VALUE OF 1.0 WITHIN THE
WARM SECTOR DURING THIS TIME. THEREFORE...ISOLATED SEVERE CONVECTION
WILL BE A CONCERN MONDAY MORNING/AFTERNOON...ESP ACROSS THE
PIEDMONT.

FINALLY...ALTHOUGH THE COLD FRONT IS EXPECTED TO MOVE EAST OF THE
AREA BY MONDAY EVENING...THE UPPER TROUGH AXIS WILL REMAIN WELL TO
THE WEST. SUPPORTING CONTINUED PRECIP CHANCES INTO EARLY TUESDAY.
COLD AIR FILTERING INTO THE MOUNTAINS WOULD FORCE A TRANSITION TO
SNOW WITH ANY PRECIP FALLING IN THE HIGHER ELEVATIONS FROM LATE
EVENING ON. DRYING WILL FINALLY OVERTAKE THE AREA BY LATE TUE...WITH
A RETURN TO COLD/DRY CONDITIONS EXPECTED BY DAY 7.

&&

.AVIATION /03Z THURSDAY THROUGH MONDAY/...
AT KCLT AND ELSEWHERE...MOISTURE AND ISENTROPIC UPGLIDE WILL
INCREASE ACRS THE WRN CAROLINAS AND NE GA AHEAD OF AN APPROACHING
COLD FRONT. THE ALREADY LOW MVFR TO IFR CIGS BEING REPORTED AROUND
THE REGION WILL THUS HAVE LITTLE CHANCE OF IMPROVING
OVERNIGHT...DESPITE BREAKS HERE AND THERE IN THE LOW CLOUD DECK
NOTED AS OF 00Z. CONDITIONS SHOULD GRADUALLY WORSEN OVERNIGHT AND
MOST SITES SHOULD SEE LIFR LOCK IN AFTER MIDNIGHT IF NOT SOONER.
CHANCE OF SHOWERS EXISTS THRU THE PERIOD AT ALL SITES BUT IS TOO LOW
TO MENTION UNTIL AFTER DAYBREAK. SLOW IMPROVEMENT EXPECTED BY MID
MORNING WITH GUIDANCE SUGGESTIVE OF MVFR CIGS BY MIDDAY AND PERHAPS
EVEN VFR AT TIMES IN THE AFTN. SOUTHERLY WINDS BETWEEN ATLANTIC HIGH
PRESSURE AND LOW PRESSURE OVER ONTARIO CANADA.

OUTLOOK...AN ACTIVE PATTERN IS EXPECTED ACROSS THE REGION THIS WEEK.
RESTRICTIVE CEILINGS EACH NIGHT THIS WEEK...ESPECIALLY ACROSS THE
MTNS CAN BE EXPECTED. A LARGE SYSTEM IS EXPECTED TO TRACK OVER THE
SOUTHEAST U.S. THIS WEEKEND...POSSIBLY RESULTING IN A LONG DURATION
OF RESTRICTIVE CEILINGS AND/OR VIS.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       MED   78%     MED   68%     MED   73%     HIGH  87%
KGSP       MED   75%     HIGH  86%     HIGH  83%     HIGH 100%
KAVL       MED   75%     HIGH  97%     HIGH  88%     HIGH  89%
KHKY       HIGH  82%     HIGH  84%     HIGH  86%     HIGH 100%
KGMU       MED   77%     HIGH  86%     HIGH  82%     HIGH 100%
KAND       HIGH  91%     HIGH  92%     HIGH  93%     HIGH 100%

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 THURSDAY DEC 5TH...

AVL...72 IN 1998
CLT...75 IN 1998
GSP...73 IN 1998

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...NED/WIMBERLEY
SHORT TERM...RWH
LONG TERM...JDL
AVIATION...WIMBERLEY
CLIMATE...DEO