000
FXUS62 KGSP 100238
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
938 PM EST MON DEC 9 2013

.SYNOPSIS...
AN AREA OF PERSISTENT CONVERGENCE WILL LINGER OVER THE REGION
TONIGHT THROUGH TUESDAY BRINGING MORE SHOWERS TO THE AREA.
RELATIVELY COLD AND DRY HIGH PRESSURE IS THEN EXPECTED TO MOVE BACK
INTO THE CAROLINAS FROM THE WEST LATE TUESDAY AND INTO WEDNESDAY AND
REMAIN OVER THE REGION THROUGH FRIDAY.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 935 PM...WIDESPREAD RAIN REMAINS LIMITED TO THE SRN CWFA
BORDER. REGIONAL RADAR SHOWS ANOTHER AREA OF RAIN SPREADING ACROSS
NRN AL AND MOVING THIS WAY. THIS RAIN IS WHAT THE GUIDANCE SHOWS
MOVING BACK IN OVERNIGHT AHEAD OF SIGNIFICANT FORCING AND LOW LEVEL
WAA. HAVE TRENDED THE POP IN THIS DIRECTION. ALSO...EXPECT SLIGHT
WARMING TO DEVELOP ACROSS THE MTNS AS THE WAA KICKS IN. THEREFORE...
DO NOT EXPECT ANY WINTER P-TYPE PROBLEMS OVERNIGHT. NEARLY STEADY
TEMPS EXPECTED ELSEWHERE. PATCHY DENSE FOG HAS DEVELOPED OVER THE
FOOTHILLS AND PORTIONS OF THE PIEDMONT AND UPSTATE. WILL ISSUE AN
SPS FOR NOW. MAY NEED A DENSE FOG ADV LATER IF IT BECOMES MORE
WIDESPREAD AND LESS VARIABLE. THAT SAID...AS RAIN MOVES IN...VSBY
MAY ACTUALLY INCREASE AS THE RAIN AND WIND MIXES THE ATMOS
DIMINISHES THE DENSE FOG.

AS OF 645 PM...WIDESPREAD RAIN MOVING EAST OF THE AREA...BUT LOW
CLOUDS REMAIN OUTSIDE OF THE MTNS. EXPECT THE CLOUDS TO FILL BACK IN
OVER THE MTNS AND CONTINUE ELSEWHERE OVERNIGHT AS ISENTROPIC LIFT
AND LOW LEVEL WAA BRING WIDESPREAD PRECIP BACK INTO THE AREA FROM
THE SW. TEMPS WILL REMAIN NEARLY STEADY OVERNIGHT...BUT MAY COOL
OVER THE HIGHER ELEVATIONS TOWARD MORNING. STILL EXPECT THE FRONT TO
MOVE EAST OF THE AREA BY TUE AFTERNOON TAKING THE PRECIP WITH IT.
GUIDANCE CAME IN A LITTLE COOLER OVER THE MTNS...SO STILL EXPECT
PRECIP TO END AS SNOW SHOWERS OVER THE HIGHER ELEVATIONS. HOWEVER...
DO NOT EXPECT ANY SIGNIFICANT ACCUMS. DO EXPECT VERY GUSTY WINDS TO
DEVELOP ACROSS THE MTNS AFTER FROPA...WITH GENERALLY LOW END GUSTS
OUTSIDE OF THE MTNS. SKIES SHUD CLEAR DURING THE AFTERNOON TO
FINALLY ALLOW SUNSHINE ACROSS MOST OF THE AREA.

PREVIOUS FORECAST...A WIDE BAND OF PRECIP STREAMING NE ACROSS THE
PIEDMONT MIGHT MAKE A BIT MORE EASTWARD PROGRESS BEFORE WEAKENING
LATE IN THE DAY. THIS WILL FORCE A VERY HIGH POP ACROSS THE AREA
ALONG AND E OF I-85...BUT THE PRECIP CHANCES CAN BE LOWERED OVER THE
MTNS AT LEAST TEMPORARILY. TEMPS STILL IN FLUX. HAVE NOT GIVEN UP ON
A LATE AFTERNOON TEMP SURGE ONCE THE PRECIP BAND WEAKENS OR MOVES
EAST.

THE MODELS ARE FAIRLY CONSISTENT FOR TONIGHT IN BRINGING ANOTHER
ROUND OF WARM ADVECTION AND UPGLIDE AT LOW LEVELS AS ANOTHER SURGE
OF THE LOW LEVEL JET PASSES THROUGH IN THE EARLY MORNING HOURS. A
LULL IN THE ACTION MAY PERSIST THROUGH THE MIDDLE PART OF THE
EVENING AND BEYOND...BUT MOIST UPGLIDE SHOULD RENEW BY 06Z OR SO.
THIS CALLS FOR BRINGING THE PRECIP CHANCES BACK UP INTO THE
CATEGORICAL RANGE IN THE PRE-DAWN HOURS. PRECIP AMOUNTS LOOK
RELATIVELY BENIGN AND WITH THE WARM ADVECTION THE TEMPS SHOULD
REMAIN ABOVE FREEZING. IN FACT...AT SOME SITES THE TEMP WILL GO UP
OVERNIGHT. THE COLD FRONT WILL MOVE ACROSS THE REGION IN THE MID TO
LATE MORNING AND THE LOW LEVEL JET WILL CARRY THE LOW LEVEL FORCING
OFF TO THE NORTHEAST BY MIDDAY. THE ARRIVAL OF THE SHORT WAVE WILL
BRING SOME MID LEVEL FORCING THAT COULD HELP HOLD THE PRECIP IN
THROUGH MIDDAY...BUT INDICATIONS ARE THAT PRECIP SHOULD WIND DOWN
QUICKLY BY OR DURING THE EARLY PART OF THE AFTERNOON. COLD AIR WILL
FILTER INTO THE MTNS AS THE PRECIP IS ENDING...WHICH WILL AFFORD A
BRIEF WINDOW OF OPPORTUNITY FOR NW FLOW UPSLOPE SNOW. AMOUNTS AGAIN
SHOULD BE MINIMAL...SO PERHAPS ONLY A FEW OF THE HIGHER PEAKS MIGHT
GET UPWARDS OF AN INCH BEFORE IT ENDS. TEMPS WILL REACH A MIDDAY
HIGH BEFORE DROPPING IN THE AFTERNOON BEHIND THE FRONT.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 240 PM EST MONDAY...MODELS IN GOOD AGREEMENT ON NEARLY ZONAL
UPPER PATTERN PERSISTING ACROSS THE SE TUE NIGHT INTO WEDNESDAY
NIGHT. A LOW AMPLITUDE UPPER TROUGH WILL SWING ACROSS THE REGION
DURING THE DAY ON THURSDAY...AND OFF THE ATLANTIC COAST BY THURSDAY
NIGHT.

AT THE SURFACE...DRY CANADIAN HIGH PRESSURE WILL BUILD IN FROM THE
NW ON TUESDAY NIGHT AND LINGER THROUGH WEDNESDAY. WITH TIGHT
PRESSURE GRADIENT...GUSTY COLD AIR ADVECTION NW WINDS WILL CONTINUE
MAINLY ACROSS THE NC MTNS ZONES AT LEAST THROUGH LATE TUESDAY NIGHT.
DRY CONDITIONS WILL PREVAIL ON WEDNESDAY AS THE HIGH SETTLES JUST TO
OUR NORTH. BY WEDNESDAY NIGHT...A DRY COLD FRONT WILL QUICKLY
APPROACH THE SOUTHERN APPALACHIANS FROM THE NW AS THE HIGH WEAKENS
AND SHIFT EAST OF THE AREA. THE FRONT WILL THEN CROSS THE REGION
THROUGH EARLY THURSDAY MORNING WITH ANOTHER CANADIAN HIGH BUILDING
IN BEHIND THE FRONT ON THURSDAY. ATMOS LOOKS TO BE TOO DRY FOR ANY
PRECIP DURING THE FROPA AND NONE OF THE MODELS HAVE ANY QPF RESPONSE
FROM IT. TEMPERATURES WILL RUN AROUND 5-7 DEGREES BELOW NORMAL
THROUGH THE PERIOD.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 230 PM MONDAY...MODELS GENERALLY AGREE THAT A SOUTHERN STREAM
SHORTWAVE TROF WILL EJECT INTO THE STERN PLAINS LATE IN THE
WEEK...BRINGING PRECIP CHCS BACK INTO THE AREA FOR THIS WEEKEND.
THERE WAS STILL A LOT OF SPREAD IN THE GEFS AND ECWMF ENS ON THE
TIMING OF THE 500 MB TROF AXIS...AND TO A LESSER EXTENT THE
AMPLITUDE. HOWEVER...THE 12Z OP GFS/CMC LINES UP BETTER WITH THE 00Z
ECMWF...AND ALL THE GUIDANCE HAS SOME SORT OF CYCLOGENESIS INVOF THE
TX PANHANDLE...THEN THE LOW TRACKING ACRS THE SOUTHEAST STATES
FRIDAY INTO FRIDAY NIGHT. STRONG UPR LVL DIVERGENCE SHUD BE COUPLED
WITH STOUT 850 MB WAA MOST LIKELY DURING THE DAY ON SATURDAY.
GRANTED...THERE IS STILL MINOR TIMING DIFFERENCE OF HIGHEST POPS.
HOWEVER...I HAVE BUMPED UP POP TO SOLID LIKELY FOR SATURDAY. THE LOW
WILL QUICKLY TRACK NE ALONG THE SPINE OF THE APPALACHIANS TO NEW
ENGLAND BY 06Z SUNDAY. SO WHILE WE SHUD SEE DECENT COVERAGE OF
PRECIP WITH GOOD RAIN RATES...THE DURATION SHUD NOT BE ENUF TO
WARRANT MUCH OF A FLOOD THREAT. WITH THAT SAID...THE 00Z AND 12Z
ECMWF ARE HEAVIEST WITH QPF TOTALS...RANGING FROM 2-3" IN A 24 HOUR
PERIOD ALONG THE I-85 CORRIDOR. SO PERHAPS IF GUIDANCE CONTINUES TO
DEPICT THESE KIND OF RAINFALL TOTALS...A HEAVY RAIN THREAT MAY BE
WARRANTED IN THE HWO WITHIN THE NEXT COUPLE DAYS.

FOR NOW...THE MAIN CONCERN WITH THIS SYSTEM WILL BE PRECIP TYPE AT
THE ONSET LATE FRIDAY NIGHT AND ON THE BACK EDGE SATURDAY NIGHT INTO
SUNDAY. USING THE BOURGOUIN TECHNIQUE OFF THE 12Z GFS
PROFILES...THERE IS A WINDOW OF A FEW HOURS OF FREEZING RAIN IN THE
NRN MTNS...SIMILAR TO WHERE SOME ICING OCCURRED WITH THE LAST STORM.
IT SHUD BE NOTED THAT THE CMC AND ECMWF PARTIAL THICKNESSES ARE
SIMILAR TO THE GFS. FROM THERE...GUIDANCE IN GOOD AGREEMENT THAT THE
STRONG WAA SHUD BRING ALL TEMPS ABOVE FREEZING BY MIDDAY
SATURDAY...WHEN THE HEAVIEST PRECIP SHUD FALL. SO AGAIN...CONFIDENCE
ON EVEN ADVISORY LVL ICE ACCUM IS TOO LOW TO MENTION IN THE HWO AT
THIS TIME. GUIDANCE ALSO SHOWS SOME LINGERING MOISTURE WITH FALLING
THICKNESSES SATURDAY NIGHT ALONG THE TN BORDER. SOME LIGHT SNOW
ACCUM ARE POSSIBLE...BUT NOT EXPECTING ANY SUBSTANTIAL NW FLOW SNOW
ACTIVITY BEHIND THE SYSTEM. SUNDAY NIGHT AND MONDAY LOOK DRY WITH
BELOW NORMAL TEMPS.

&&

.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
AT KCLT...LIFR CIGS AND VFR VSBY WITH PATCHY RAIN EXPECTED THRU THE
EVENING...BUT CANNOT RULE OUT BRIEF IMPROVEMENTS. EXPECT LIFR CIGS
AND MVFR VSBY IN RAIN AND DRIZZLE OVERNIGHT AND THRU THE MORNING
TUE...WITH POSSIBLY WORSE CONDITIONS FROM TIME TO TIME. LOW LEVEL
MOISTURE IS SCOURED OUT FOR THE AFTERNOON AS A COLD FRONT CROSSES
THE AREA. THIS WILL BRING QUICKLY IMPROVING CONDITIONS AND NWLY
WINDS. LOW END GUSTS ARE POSSIBLE ONCE THE FRONT MOVES THRU.

ELSEWHERE...SIMILAR CONDITIONS AS KCLT. KHKY WILL SEE IFR FOG...AND
IFR FOG DEVELOPS AT KAND. GUSTS ARE MORE LIKELY AT THESE SITES AFTER
FROPA...WITH STRONG GUSTS DEVELOPING AT KAVL FOR THE AFTERNOON.
WINDS WILL DIMINISH BY THE END OF THE PERIOD...BUT REMAIN GUSTY AT
KAVL.

OUTLOOK...VFR CONDITIONS WITH DIMINISHING WINDS TUESDAY NIGHT. DRY
HIGH PRESSURE WILL SET UP THROUGH WEDNESDAY AND CONTINUE THROUGH
LATE WEEK...WITH VFR CONDITIONS.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z
KCLT       MED   65%     HIGH  80%     MED   79%     HIGH 100%
KGSP       MED   74%     HIGH  80%     HIGH  81%     HIGH 100%
KAVL       HIGH  80%     MED   74%     MED   75%     HIGH 100%
KHKY       MED   68%     MED   76%     MED   75%     HIGH 100%
KGMU       MED   73%     HIGH  81%     HIGH  85%     HIGH 100%
KAND       MED   63%     MED   74%     MED   70%     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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...JOH
NEAR TERM...PM/RWH
SHORT TERM...JOH
LONG TERM...ARK
AVIATION...RWH