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000
FXUS62 KGSP 111933
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
233 PM EST WED DEC 11 2013

.SYNOPSIS...
RELATIVELY COLD AND DRY HIGH PRESSURE WILL CONTINUE OVER OUR REGION
THROUGH FRIDAY AND THEN MOVE OFF THE CAROLINA COAST. ANOTHER LOW
PRESSURE SYSTEM SHOULD ARRIVE FROM THE WEST ON SATURDAY AND BRING
MORE WIDESPREAD PRECIPITATION TO THE REGION OVER THE WEEKEND. EXPECT
ANOTHER HIGH PRESSURE SYSTEM TO BRING DRY WEATHER THROUGH THE MIDDLE
OF NEXT WEEK.

&&

.NEAR TERM /THROUGH THURSDAY/...
AS OF 200 PM...A SHORTWAVE WILL DIVE THRU A BROAD UPPER TROF ACRS
THE OHIO VALLEY TONIGHT...CROSSING THE CENTRAL APPALACHIANS THURSDAY
MORNING. THE ENERGY WILL PUSH A DRY RE-ENFORCING COLD FRONT THRU THE
AREA LATE THIS EVENING THRU THE OVERNIGHT...USHERING IN BREEZY NWLY
WINDS ACRS THE HIGH TERRAIN THAT WILL CONTINUE THRU THE DAY
THURSDAY. TEMPS WILL DROP INTO THE TEENS TO LOWER 20S IN THE
MTNS...AND MID TO UPPER 20S IN THE PIEDMONT. THEN WITH ONGOING 850
MB CAA THRU THE DAY...DESPITE SUNNY SKIES...EXPECT TEMPS TO ONLY
RISE INTO THE 20S TO LOWER 30S IN THE MTNS...AND MAINLY IN THE 40S
ACRS THE PIEDMONT (EXCEPT FOR A FEW LOW 50S IN THE UPPER SAVANNAH
VALLEY).

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY NIGHT/...
AS OF 230 PM WEDNESDAY...THE MAIN PROBLEM FOR THIS FCST IS THE NEXT
WEATHER SYSTEM EXPECTED TO AFFECT THE WESTERN CAROLINAS OVER THE
WEEKEND. THURSDAY NIGHT AND FRIDAY WILL BE QUIET AS AN UPPER RIDGE
MOVES A SURFACE HIGH ACROSS THE CAROLINAS...EVEN THOUGH WARM
ADVECTION AND ISENTROPIC LIFT WILL BE WELL UNDERWAY ON FRIDAY
AFTERNOON. TEMPS WERE KEPT CLOSE TO GUIDANCE.

THE WEATHER SITUATION GETS MORE COMPLICATED FRIDAY NIGHT. FOR
OPENERS...THE MODEL SOLUTIONS HAVE SLOWED DOWN THE SHORT WAVE
EJECTING FROM THE SRN PLAINS...AND NOW THE CONSENSUS OF THE GUIDANCE
HAS THIS FEATURE LIFTING UP TO THE OH VALLEY BY SATURDAY MORNING.
LOW LEVEL ISENTROPIC UPGLIDE AND WARM ADVECTION SHOULD STRENGTHEN
OVERNIGHT...BUT MOISTURE DOES NOT ARRIVE UNTIL SOME TIME CLOSER TO
06Z SATURDAY. EVEN THEN...THE EARLY PRECIP PRODUCTION WILL HAVE A
HARD TIME MAKING IT TO THE GROUND WITH DRY AIR NEAR THE SURFACE.
THUS...IT WOULD APPEAR THAT PRECIP ONSET WILL PROBABLY NOT HAPPEN
UNTIL SOME TIME AFTER MIDNIGHT OVER THE WRN ZONES...AND CLOSER TO
DAYBREAK E OF I-85...WHICH THE FCST WILL REFLECT. THIS GIVES US EVEN
MORE TIME FOR WARM ADVECTION TO KEEP TEMPS ABOVE FREEZING. THE MODEL
TREND APPEARS TO BE FOR WARMER LOW LEVELS. IN FACT...PARTIAL
THICKNESSES SUGGEST THAT PRECIP WILL BE NEARLY ALL RAIN THROUGH
SATURDAY MORNING. THERE MIGHT BE A BRIEF WINDOW FOR FREEZING RAIN
OVER MOSTLY THE NRN MTNS AS PRECIP BEGINS AROUND 06Z SATURDAY...BUT
THE CHANGEOVER TO ALL RAIN SHOULD BE NEARLY COMPLETE BY 12Z
SATURDAY. THE EXCEPTION WILL BE THE HIGHEST MTN PEAKS THAT ARE ABOVE
THE WARM NOSE...SUCH THAT ELEVATIONS ABOVE 5K FEET MIGHT SEE SEVERAL
HOURS OF SNOW BEFORE CHANGING TO RAIN NO LATER THAN 15Z. PRECIP
CHANCES RAMP UP TO CATEGORICAL ON SATURDAY WITH A COLD RAIN EXPECTED
ACROSS THE ENTIRE REGION...THANKS TO A HYBRID SORT OF WEDGE IN
BETWEEN MILLER B-TYPE SFC LOWS. THINK THE HEAVIER PRECIP AND THUNDER
POTENTIAL WILL REMAIN TO OUR SOUTH...IN THE WARMER AIR ALONG A
COASTAL FRONT THAT IS NOT EXPECTED TO PENETRATE FAR ENOUGH NWD TO
REACH THE SRN ZONES. ONCE THE LOWS PASS...THE WEDGE WILL DRAIN AWAY
SATURDAY NIGHT AND PRECIP CHANCES WILL SLOWLY MOVE EAST. THERE
SHOULD BE A PERIOD OF NW FLOW PRECIP ON SUNDAY MORNING...WHICH
SHOULD BE SOME SORT OF RAIN CHANGING TO A WINTRY MIX AS THE COLDER
AIR COMES IN AFTER MIDNIGHT. THE PROBLEM IS THAT THE MOISTURE WILL
BE SHALLOW...SO THIS COULD BE MORE OF A LIGHT FREEZING RAIN IN SOME
SPOTS ON THE TN BORDER. THE EVENT SHOULD END EARLY SUNDAY
EVENING...WITH DRY HIGH PRESSURE BUILDING IN FROM THE WEST SUNDAY
NIGHT.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 150 PM EST WEDNESDAY...AT 12Z MONDAY THE AXIS OF THE 500MB
TROUGH IS ROUGHLY ALONG THE SPINE OF THE APPALACHIANS WITH MOST OF
THE ACTION ALONG THE CANADIAN BORDER...OTHERWISE DRY ACROSS THE
COUNTRY. A STRONG SHORTWAVE CROSSES THE GREAT LAKES TUESDAY AND
TUESDAY NIGHT.  THE CURRENT GFS KEEPS ALL AFFECTS OF THIS WELL NORTH
AS WE WOULD HAVE NEARLY ZONAL FLOW.  THE 00Z AND THE NEW 12Z WED
ECMWF HAS A DEEPER TROUGH AND THE AXIS OF THE SHORTWAVE CROSSES THE
MTNS AROUND 06Z WED WITH BATCHES OF SNOW SHOWERS CROSSING WEST
VIRGINIA. IN CONSIDERATION OF POSSIBLE AFFECTS FROM THIS SHORTWAVE
LATE TUESDAY NIGHT...RAISED CLOUD COVER A BIT THIS PERIOD FOR THE
MTNS. MEDIUM RANGE MODELS DIVERGE SOME ON THE DAY 7 WEATHER WITH
ECMWF DEVELOPING A GREATER AMPLITUDE 500MB RIDGE OVER THE EASTERN
TWO THIRDS OF THE NATION.  THE GFS AND ECMWF ARE BOTH DIGGING A
TROUGH IN SOME FORM OVER THE WEST COAST. THE ECMWF KEEPS OUR REGION
DRY THROUGH THE FOLLOWING WEEKEND WHILE THE GFS PROJECTS THE WEEKEND
BEFORE CHRISTMAS TO BE SOGGY FOR THE SE STATES.  I SEE THE CURRENT 8
TO 14 DAY OUTLOOK HAS OUR ENTIRE REGION IN ABOVE NORMAL PRECIP AND
NEAR NORMAL TEMPS.

CURRENT MEDIUM RANGE HAS A LITTLE BELOW NORMAL TEMPS DAY 6 THROUGH
NEW DAY 7.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
AT KCLT...PRIMARILY A WIND FCST FOR THE NEXT 24 HOURS. PATCHY CIRRUS
MAY BRIEFLY INCREASE TO A THIN CIG THIS EVENING. BUT
OTHERWISE...FEW250 OR SKC. WINDS WILL FAVOR A LGT SWLY DIRECTION
THIS AFTN INTO THIS EVENING...THEN TURN BACK OUT OF THE NORTH AROUND
06Z WITH THE PASSAGE OF A DRY COLD FRONT. N/NE WINDS PICK UP TO NEAR
10 KTS BY MID MORNING THURSDAY.

ELSEWHERE...JUST SOME PATCHY CIRRUS THIS AFTN...WITH LGT SW WIND
EAST OF THE MTNS...AND NW AT KAVL. WINDS WILL SHIFT OUT OF THE N/NW
AT ALL SITES BEHIND THE PASSAGE OF A DRY COLD FRONT OVERNIGHT
TONIGHT...WITH A BRIEF PERIOD OF INCREASED CIRRUS. CHANNELED VALLEY
WINDS SHUD BECOME GUSTY BY DAYBREAK THURSDAY AT KAVL...AND REMAIN
GUSTY THRU END OF TAF PERIOD.

OUTLOOK...DRY HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH
FRIDAY. A STORM SYSTEM WILL ARRIVE FROM THE WEST BY SATURDAY WITH
RESTRICTIONS ONCE AGAIN LIKELY. CONDITIONS WILL DRY OUT FROM THE SW
ON SUNDAY...WITH DRY HIGH PRESSURE RETURNING FOR MONDAY.

CONFIDENCE TABLE...

            19-01Z        01-07Z        07-13Z        13-19Z
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%
KAND       HIGH 100%     HIGH 100%     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...DEO
NEAR TERM...ARK
SHORT TERM...PM
LONG TERM...DEO
AVIATION...ARK