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000
FXUS62 KGSP 100603
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
103 AM EST TUE DEC 10 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 TONIGHT/...
AS OF 1245 AM EST...WATER VAPOR IMAGERY DEPICTS A SHORTWAVE MOVING
TOWARD THE MS RIVER VALLEY EARLY THIS MORNING. THIS FEATURE IS
GENERATING CONSIDERABLE SHOWER COVERAGE ON RADAR ACROSS NW GA
UPSTREAM OF OUR SRN MOUNTAINS...AND IT SHOULD SPAWN ADDITIONAL
UPGLIDE FORCED PRECIP OUT OVER THE CWFA THROUGH DAYBREAK. IN
ADDITION...SFC LOW PRES RESPONDING TO THE WEAK FORCING WILL DEVELOP
ALONG THE FRONTAL BOUNDARY OVER THE DEEP SOUTH EARLY THIS MORNING
AND LIKELY RIDE UP INTO THE WRN CAROLINAS BY DAYBREAK TO CREATE A
LOCALIZED QPF MAXIMUM IN THE SRN MTNS AND NEARBY FOOTHILLS.
INSTABILITY APPEARS QUITE LIMITED ACROSS THE REGION THIS MORNING
AHEAD OF THESE FEATURES...BUT ISOLD TSTMS COULD SURVIVE INTO THE SW
MTNS. THE DEEPEST MOISTURE WILL AFFECT THE SW MTNS CIRCA 09Z...MOVE
TO THE BLUE RIDGE BY 12Z...THEN OUT TO THE PIEDMONT BY 15Z BEFORE
CLEARING THIS AFTN AS THE SHEARING UPPER WAVE GETS ABSORBED BACK
INTO THE NRN STREAM AND PASSES MAINLY N OF OUR FORECAST AREA.

FOLLOWING THE WAVE PASSAGE AND ASSOCIATED FROPA...COLD ADVECTION
WILL ALLOW SNOW LEVELS TO PLUNGE ACROSS THE WRN MOUNTAINS BY LATE
MORNING THROUGH THE AFTN...BUT WITH QPF DRYING UP RAPIDLY TO LIMIT
SNOW SHOWERS. IN ADDITION...ANY NW FLOW MOISTURE THIS AFTERNOON WILL
BE SHALLOW AND BRIEF. WINDY CONDITIONS WILL KICK UP IN THE COLD
ADVECTION THIS AFTERNOON AND EVENING BEFORE THE GRADIENT DIMINISHES
OVERNIGHT AS SFC HIGH PRES SETTLES OVER THE SRN APPALACHIANS. FAIRLY
STRONG MID LEVEL FRONTOGENESIS ALONG WITH A 45 KT JET IN THE BEST
COLD ADVECTION WILL ALLOW WIND GUSTS TO FLIRT WITH ADVISORY CRITERIA
FOR THE CENTRAL AND NRN MOUNTAINS. A WIND ADVISORY COULD BE NEEDED
FOR THE AFTN AND EVENING THERE.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...
AS OF 100 AM EST TUESDAY...DRY AND COOL CONDITIONS WILL PREVAIL
THROUGH THE SHORT TERM PERIOD AS ZONAL FLOW ALOFT COMBINES WITH COLD
ADVECTION AT THE SURFACE AS HIGH PRESSURE SETTLES ACROSS THE OHIO
VALLEY BY WEDNESDAY MORNING.  MEANWHILE...UPPER TROF WILL CONTINUE
TO DIG ACROSS THE UPPER MIDWEST AS A COLD FRONT PUSHES SOUTHEAST
INTO THE MID MISSISSIPPI RIVER VALLEY.  AS FOR NORTHEAST GA AND THE
WESTERN CAROLINAS...CLEAR SKIES AND BELOW NORMAL TEMPERATURES WILL
CONTINUE THROUGH THE DAY ON WEDNESDAY AS HIGH PRESSURE DOMINATES.
NORTHERN STREAM UPPER TROF WILL EJECT TO THE NORTHEAST OVERNIGHT
WEDNESDAY AND INTO THURSDAY MORNING.  MODELS REMAIN CONSISTENT WITH
REGARDS TO MAXIMUM DEEP LAYER FORCING/MOISTURE ASSOCIATED WITH THE
TROF AXIS PASSING BY WELL TO THE NORTH OF THE SOUTHERN APPALACHIANS
REGION.  THE TRAILING COLD FRONT IS LIKELY TO ENTER THE WESTERN NC
MOUNTAINS EARLY ON THURSDAY MORNING AND CONTINUE THROUGH THE
REMAINDER OF THE FORECAST AREA THROUGH THE AFTERNOON HOURS.  AT THIS
TIME...OTHER THAN SLIGHT INCREASES IN CLOUD COVER ASSOCIATED WITH
WEAK UPSLOPE FORCING ALONG THE HIGH TERRAIN...NO SIGNIFICANT IMPACTS
ARE EXPECTED WITH THIS FROPA.

BEHIND THE FRONT...CANADIAN HIGH PRESSURE WILL FILL IN FROM THE WEST
LEADING TO CONTINUED COLD ADVECTION PATTERN.  TEMPERATURES DURING
THE AFTERNOON HOURS ON THURSDAY WILL STRUGGLE TO TOP THE UPPER 40S
ACROSS THE PIEDMONT WITH MUCH COOLER TEMPERATURES IN THE HIGH
TERRAIN WHERE INCREASED NORTHWESTERLY WINDS WILL YIELD WIND CHILLS
IN THE SINGLE DIGITS.  TEMPERATURES WILL FALL OFF DIURNALLY AFTER
SUNSET THURSDAY EVENING LEADING TO OVERNIGHT LOWS WELL BELOW NORMAL
FOR THE ENTIRE REGION.

&&

.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 /06Z TUESDAY THROUGH SATURDAY/...
AT KCLT...CONDITIONS WILL BE QUITE VARIABLE 06Z TO 09Z AS THE BACK
EDGE OF SHOWERS FLIRTS WITH THE AIRFIELD AND CREATES JUST ENOUGH
MIXING FOR MVFR TEMPO LIFR CONDITIONS. EXPECT CIGS TO TRANSITION
DOWN TOWARD MORE SOLID LIFR AFTER 09Z AND REMAIN SUCH UNTIL FROPA
TODAY CAN PRODUCE SCOURING W TO NW FLOW AROUND 17Z. STOUT SW FLOW IS
EXPECTED JUST ABOVE THE SFC THIS MORNING...BUT WITH SHEAR LAYERS TOO
GRADUAL FOR A LLWS MENTION. EXPECT GUSTS TO ONSET QUICKLY WITH THE
COLD ADVECTION THIS AFTERNOON AND THEN DIMINISH TOWARD EVENING WITH
WEAK DECOUPLING AS SKIES CONTINUE TO CLEAR.

ELSEWHERE...RAIN AND SHOWERS WILL STEADILY FILL BACK IN FROM THE
WEST THROUGH THE EARLY MORNING HOURS AS LOW PRESSURE RIDES UP A
STALLED FRONT TOWARD THE REGION AND A WEAK UPPER SHORTWAVE
APPROACHES FROM THE WEST. EXPECT MAINLY LIFR CONDITIONS AT MOST
SITES...BUT WITH HIGHLY VARYING CONDITIONS WITH MIXING FROM ANY
SHOWERS...AND WITH MAINLY MVFR TEMPO IFR AT KAVL. WINDS WILL TURN
QUICKLY NORTHWEST WITH FROPA TODAY...USHERING IN GUSTS NEAR 30 KT AT
KAVL BY 17Z...AND GUSTS INTO THE LOWER 20S AT THE FOOTHILL SITES.
WINDS WILL DECOUPLE THIS EVENING ALL BUT KAVL.

OUTLOOK...DRY HIGH PRESSURE WILL SET UP OVER THE REGION WED THROUGH
FRI. A STORM SYSTEM WILL ARRIVE FROM THE WEST BY SATURDAY WITH
RESTRICTIONS LIKELY.

CONFIDENCE TABLE...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       HIGH  85%     MED   78%     HIGH  96%     HIGH 100%
KGSP       HIGH  85%     MED   64%     HIGH 100%     HIGH 100%
KAVL       MED   79%     MED   67%     HIGH  92%     HIGH 100%
KHKY       HIGH  85%     MED   68%     HIGH 100%     HIGH  95%
KGMU       HIGH  84%     MED   66%     HIGH 100%     HIGH 100%
KAND       HIGH  85%     MED   61%     HIGH 100%     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...HG
SHORT TERM...JOH
LONG TERM...ARK
AVIATION...HG