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000
FXUS62 KGSP 131133
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
633 AM EST FRI DEC 13 2013

.SYNOPSIS...
DRY HIGH PRESSURE WILL CONTINUE OVER THE REGION TODAY AND THEN MOVE
OFF THE CAROLINA COAST BY LATE TONIGHT. A LOW PRESSURE SYSTEM IS
EXPECTED TO ARRIVE FROM THE WEST ON SATURDAY BRINGING 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 TONIGHT/...
AS 630 AM...GOING FCST ON TRACK. ONLY UPDATES WERE FOR CURRENT
CONDITIONS.

AS OF 230 AM...CIRRUS WILL INCREASE AND COVERAGE AND THICKEN THRU
THE DAY AS MOISTURE MOVES IN IN THE NEARLY ZONAL FLOW OVER THE AREA.
THIS WILL KEEP HIGHS A COUPLE OF DEGREES BELOW NORMAL DESPITE THE
WARM THICKNESSES OVER THE AREA AND SWLY FLOW AROUND THE DEPARTING
SFC HIGH.

THIS EVENING...AN UPPER LOW OVER THE SWRN CONUS OPENS UP AND MOVES
TOWARD THE AREA. HOWEVER...GOOD LOW LEVEL MOISTURE AND ISENTROPIC
LIFT HOLD OFF UNTIL AFTER MIDNIGHT. THEREFORE...EXPECT THE CWFA TO
REMAIN DRY UNTIL AFTER MIDNIGHT. WINDS OVER THE MTNS BECOME
BREEZY...ESPECIALLY AT THE RIDGE TOPS...WHILE WINDS BEGIN TO TURN
NELY OUTSIDE OF THE MTNS AS A NON-CLASSICAL CAD DEVELOPS.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 3 AM FRI...PICKING UP AT 06Z SATURDAY...BROAD HIGH PRESSURE
WILL BE CENTERED OFF THE ATLANTIC COAST UNDER A NEARLY ZONAL BUT
SLIGHTLY CONFLUENT UPPER PATTERN. STRONG SHORTWAVE WILL BEGIN LIFTING
FROM THE SRN PLAINS INTO THE MISSISSIPPI DELTA REGION AS A LARGER
TROUGH BEGINS TO OCCUPY THE MIDDLE THIRD OF THE CONUS. S/W ALONG WITH
ATTENDANT SFC LOW WILL SHOOT UP THE OHIO VALLEY DURING THE DAY.  LOW
TO MID LEVEL FLOW RAPIDLY TURNS SOUTHERLY AS IT APPROACHES...AND THE
RESULTANT ISENTROPIC UPGLIDE AND MSTR RETURN OVER THE COOL HIGH
PRESSURE WILL BRING A QUICK ROUND OF PRECIP BEFORE INITIAL SHORTWAVE
PUSHES ACRS THE CWFA...FOLLOWED BY DRY SLOT. UPSLOPING IN THE SRN
MTNS AND ALONG THE SRN FACING ESCARPMENT WILL CAUSE POPS TO RAMP UP
STARTING JUST AFTER 06Z SAT...SPREADING EAST AND COVERING PRACTICALLY
ALL OF THE FA BY MIDDAY BEFORE DIMINISHING FROM THE WEST.

SETUP SUGGESTS A BRIEF IN SITU WEDGE COULD REMAIN IN PLACE EARLY
SATURDAY...LEADING TO POTENTIAL PTYPE CONCERNS. MODEL CONSENSUS LOW
TEMPS SAT MRNG ARE GENERALLY VERY CLOSE TO THE FREEZING MARK...BUT
RAW MODEL WET BULB TEMPS ARE APPROX 3-5F BELOW 2M TEMPS. ICE NUCLEI
SHOULD BE AVAILABLE PER PROG SOUNDINGS FROM BOTH NAM/GFS...AND
DESPITE THE STRONG WAA THE WARM NOSE IS COOL ENOUGH IN THE NRN MTNS
THAT SOME SNOW OR SLEET COULD RESULT AT THE GROUND. FURTHER SOUTH
ANY AREAS THAT ARE BELOW FREEZING WOULD BE AT RISK FOR FZRA. TEMPS
DO WARM ENOUGH BY MIDDAY TO RETURN ALL PCPN TO LIQUID...THOUGH
CHANCES ARE DIMINISHING IN THE AREAS OF CONCERN BY THAT TIME ANYWAY.
MODEL QPF IS FAIRLY MODEST DESPITE THE STRONG LLVL JET AND UPPER
DIVERGENCE...WITH THE SYSTEM MOVING FAST AND INITIALLY OVERCOMING
DRY LLVLS. SLIGHT CONVECTIVE ENHANCEMENT NOT OUT OF THE QUESTION
THOUGH INSTABILITY ABOVE THE WARM NOSE IS NOT ENOUGH TO BE OF MUCH
CONSEQUENCE...AND CERTAINLY LOOKS TOO WEAK TO INCLUDE ANY THUNDER IN
FCST. ALL IN ALL...ICE AND SNOW AMOUNTS ARE BELOW WARNING
CRITERIA...AND GIVEN SLIGHT DIFFERENCES IN MODEL SOUNDINGS WILL
ALLOW DAY SHIFT TO MAKE AN ADVISORY DECISION.

SFC LOW UNDERGOES SECONDARY CYCLOGENESIS IN MILLER B SCENARIO
SATURDAY NIGHT...WITH LARGER UPPER TROUGH AND COLD AIR BEGINNING TO
PUSH IN. CONCERN NOW BECOMES FOR NW FLOW FROZEN PRECIP IN THE MTNS.
ONCE AGAIN...AMOUNTS LOOK LIGHT AS SATURATION NOT REACHED OVER A DEEP
LAYER. RELATIVELY WARM TEMP OF THE SFC BASED MOIST LAYER INITIALLY
SUGGESTS FZDZ OR LIGHT FZRA...BUT THE TOP OF THE LAYER COOLS AS WINDS
TAPER OFF ON SUNDAY SUGGESTING A CHANGEOVER TO SN BEFORE THE EVENT
ENDS.

SATURDAY NIGHT AND SUNDAY...AS COLD ADVECTION TAKES HOLD WINDS WILL
PICK UP ESPECIALLY IN HIGHER ELEVATIONS. A FEW GUSTS INTO THE 30S KT
ARE LIKELY THERE...WITH FREQUENT GUSTS OF 25-30. NO HEADLINES
NECESSARY AT THIS TIME.

HIGHS WILL BE COOLER SAT VS SUN IN THE PIEDMONT GIVEN THE EROSION OF
THE WEDGE...BUT COOLER SUN IN THE MTNS DUE TO THE AFOREMENTIONED CAA.
TEMPS DIP BELOW FREEZING THROUGHOUT THE CWFA BY MONDAY MORNING.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 130 AM EST FRIDAY...EXPECT DRY WEATHER AND NEAR SEASONAL
AVERAGE TEMPERATURES THROUGHOUT THE MEDIUM RANGE PERIOD.

MODELS CONTINUE TO AGREE THAT A BROAD LOW AMPLITUDE UPPER TROUGH
WILL SWING ACROSS THE EASTERN STATES MONDAY THROUGH TUESDAY WITH ITS
TROUGH AXIS PUSHING OFF THE ATLANTIC COAST BY EARLY WEDNESDAY. BY
THURSDAY...AN UPPER TROUGH WILL DEEPEN ACROSS THE WESTERN STATES
WHILE 590 DM ANTICYCLONE WILL BUILD SOUTH OF FL. THIS WILL RESULT IN
MOIST SOUTHWESTERLY FLOW ALOFT ACROSS THE REGION THROUGH THURSDAY
NIGHT.

AT THE SURFACE...HIGH PRESSURE CENTERED ACROSS THE REGION MONDAY
WILL GRADUALLY SHIFT EAST OF THE AREA THROUGH TUESDAY MORNING AS A
DRY COLD FRONT APPROACHES FROM THE NW. THE FRONT WILL THEN CROSS THE
REGION LATE TUESDAY WITH ANOTHER HIGH BUILDING IN FROM THE WEST ON
WEDNESDAY. WEDNESDAY NIGHT...A DRY BACK DOOR COLD FRONT WILL SLIP
THROUGH THE REGION AS A CANADIAN HIGH OVER THE GREAT LAKES REGION
MIGRATES INTO NEW ENGLAND. THURSDAY...THE HIGH CENTERED ACROSS THE
NE WILL RIDGE SWARD INTO THE FORECAST AREA RESULTING IN CONTINUED
DRY CONDITIONS. TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL ON
MONDAY AND WARM UP TO NEAR NORMAL BY TUESDAY.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AT KCLT AND ELSEWHERE...SFC HIGH PRES OVER THE AREA MOVES THIS
AFTERNOON. CALM WINDS BECOME LIGHT SW TODAY. CIRRUS CLOUDS WILL
INCREASE AND THICKEN DURING THE DAY. A STORM SYSTEM APPROACHES THE
AREA TONIGHT WITH LOWERING VFR CLOUDS DURING THE EVENING. WINDS TURN
SE THEN NE OUTSIDE OF THE MTNS AND SELY AT KAVL DURING THE EVENING.
LOW VFR POSSIBLE...ESPECIALLY AT THE WRN SITES. ALSO...PRECIP MAY BE
MOVING IN FROM THE WEST AS WELL. HOWEVER...DO NOT EXPECT ANY
RESTRICTIONS OR SIGNIFICANT PRECIP THRU 12Z.

OUTLOOK...THE STORM SYSTEM WILL MOVE FROM THE SRN PLAINS TO THE SRN
APPALACHIANS DURING THE DAY SAT...WHEN RESTRICTIONS IN RAINFALL WILL
BECOME MOST LIKELY. CONDITIONS WILL DRY OUT FROM THE SW ON SUNDAY...
WITH DRY HIGH PRESSURE RETURNING FOR MONDAY.

CONFIDENCE TABLE...

            11-17Z        17-23Z        23-05Z        05-11Z
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...JOH
NEAR TERM...RWH
SHORT TERM...WIMBERLEY
LONG TERM...JOH
AVIATION...RWH