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000
FXUS62 KGSP 120820 CCA
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
316 AM EST THU DEC 12 2013

.SYNOPSIS...
RELATIVELY COLD AND DRY HIGH PRESSURE WILL CONTINUE OVER THE REGION
TODAY THROUGH FRIDAY AND THEN MOVE OFF THE CAROLINA COAST. ANOTHER
LOW PRESSURE SYSTEM SHOULD 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 OF 215 AM EST...WATER VAPOR IMAGERY SHOWS A SHORTWAVE JUST WEST
OF THE APPALACHIANS EARLY THIS MORNING. THIS FEATURE...ACCOMPANIED
BY VERY LIMITED MOISTURE...WILL MOVE EAST OF THE MTNS BY 12Z. THE
MAIN IMPACT WILL BE A BRIEFLY TIGHTENING PRESSURE GRADIENT BEHIND
THE WAVE THAT WILL GENERATE GUSTY NW WINDS ACROSS THE NRN NC MTNS.
THE WINDS SHOULD REMAIN BELOW ADVISORY LEVELS. IN ADDITION...A
REINFORCING SFC COLD WILL CONTINUE TO SWEEP SE OF THE AREA BY
DAYBREAK. THIS WILL LEAVE COOL THICKNESSES IN PLACE ACROSS THE AREA
TO SUPPORT MAX TEMPERATURES 5 TO 10 DEGREES BELOW CLIMO OVER THE
FOOTHILLS AND PIEDMONT TODAY...AND 10 TO 15 DEGREES BELOW CLIMO
ACROSS THE MTNS. LITTLE MORE THAN HIGH CIRRUS IS EXPECTED
EARLY...AND THIS SHOULD MOVE OFF TO THE SE THROUGH THE DAY ALONG
WITH THE DEPARTING UPPER JET AXIS.

SFC HIGH PRES WILL BECOME CENTERED DIRECTLY OVER THE SRN
APPALACHIANS TONIGHT TO PRODUCE CLEAR SKIES AND LIGHT WINDS. THE
GOOD RADIATING CONDITIONS WILL YIELD MIN TEMPS IN THE UPPER TEENS TO
AROUND 20 IN THE MTNS...WITH SOLID 20S ACROSS THE FOOTHILLS AND
PIEDMONT OVERNIGHT.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 315 AM THURSDAY...THE SHORT TERM PERIOD WILL INITIALIZE FRIDAY
MORNING WITH HIGH PRESSURE IN PLACE ACROSS THE EAST AND AN UPPER
TROF DIGGING ACROSS THE DESERT SOUTHWEST.  THE ABOVE MENTIONED EAST
COAST RIDGE WILL SHIFT OUT TO SEA ON FRIDAY AS THE UPPER WAVE
MIGRATES EAST.  GUIDANCE CONTINUES TO AGREE WITH REGARDS TO THE
TIMING OF PRECIPITATION ONSET ASSOCIATED WITH THIS NEXT SYSTEM.
EXPECTING LIGHT SHOWERS EARLY ON SATURDAY MORNING ACROSS THE
SOUTHWEST NC AND NORTHEAST GA MOUNTAINS AS ISENTROPIC ASCENT AHEAD
OF THE PARENT LOW INCREASES.  THEREFORE...WILL CARRY CHANCE POPS
EARLY ON SATURDAY MORNING ACROSS THE WESTERN ZONES.  LOW
TEMPERATURES ON SATURDAY MORNING SHOULD BE IN THE MID TO UPPER 30S
ACROSS THE MAJORITY OF THE FORECAST AREA.  HOWEVER...GUIDANCE
CONTINUES TO INDICATE FAVORABLE FZRA TEMPERATURE PROFILES ACROSS
PORTIONS OF THE NORTHERN NC MOUNTAINS FOR A FEW HOURS EARLY SATURDAY
MORNING WITH ALL PRECIPITATION CHANGING TO RA AROUND DAYBREAK AS
WARM ADVECTION PREVAILS.  POPS WILL RAMP UP TO SOLID CATEGORICAL
LEVELS BY MIDDAY ACROSS THE ENTIRE REGION AS LIGHT TO MODERATE
SHOWERS OVERSPREAD THE REGION.

ADDITIONALLY...FORECAST SOUNDINGS INDICATE MARGINAL MID LEVEL
INSTABILITY THROUGH THE PROFILE ACROSS THE SOUTHWEST MOUNTAINS
EARLY ON SATURDAY AS THE SURFACE LOW APPROACHES AND SHEAR
MAXIMIZES.  THEREFORE...WILL MENTION CHANCES FOR ISOLATED THUNDER IN
THE FORECAST ACROSS THESE ZONES...SPREADING EAST THROUGH THE DAY AS
THE SURFACE LOW AND UPPER SUPPORT PASS THROUGH.  AS THE SYSTEM
DEEPENS AND EJECTS UP THE EAST COAST SUNDAY MORNING...POPS WILL
DECREASE FROM WEST TO EAST.  WILL KEEP MENTION OF SLIGHT/CHANCE
LEVEL POPS ACROSS THE HIGH TERRAIN ON SUNDAY AS MOISTURE WRAPS
AROUND THE DEPARTING LOW YIELDING POTENTIAL FOR A BRIEF NWFS EVENT.
NOT EXPECTING ANY SIGNIFICANT ACCUMULATIONS OUT OF EITHER THE
EARLIER ONSET FZRA...NOR THE LATER PERIOD NWFS EVENT...THUS
GENERALLY LESS THAN A TENTH OF AN INCH OF ICE ACCUMULATION AND LESS
THAN AN INCH OF SNOWFALL.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 220 AM EST THURSDAY...THE GLOBAL MODELS ARE IN GOOD AGREEMENT
WITH THE OVERALL SYNOPTIC PATTERN THROUGHOUT THE MEDIUM RANGE
PERIOD. H5 HEIGHTS WILL RISE ACROSS THE REGION ON MONDAY AS AN UPPER
TROUGH PUSHES OFF THE ATLANTIC COAST. UPPER PATTERN THEN BECOMES
QUASI-ZONAL BY MON NIGHT AND CONTINUE THAT WAY THROUGH TUESDAY. AN
UPPER TROUGH OVER THE UPPER MIDWEST TUE NIGHT IS EXPECTED TO DIG
INTO THE SOUTHERN APPALACHIANS BY WEDNESDAY...AND MOVE OFF THE
ATLANTIC COAST BY WED NIGHT.

AT THE SURFACE...BROAD HIGH PRESSURE WILL BE CENTERED ACROSS THE SE
BRINGING DRY WEATHER AND MODERATING TEMPS TO THE REGION MONDAY INTO
TUESDAY. A DRY COLD FRONT WILL THEN APPROACH FROM THE NW AND CROSSES
THE REGION ON LATE WEDNESDAY. THE GFS BRINGS LIGHT NW PRECIP TO THE
NORTHERN NC MTNS WITH THIS FEATURE WHILE THE ECMWF KEEPS MOST OF THE
AREA DRY. GIVEN THE UNCERTAINTY...HAVE MENTIONED SLIGHT CHANCE POPS
OF RAIN AND SNOW MIX OVER THE NC MTNS WED NIGHT AND KEPT ELSEWHERE
DRY. ANOTHER HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT BEYOND DAY
7. TEMPERATURES WILL START OUT 3-5 DEGREES BELOW NORMAL ON MONDAY
AND A GRADUAL MODERATING TREND EXPECTED THROUGH WEDNESDAY.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT...A WEAK COLD FRONT NOW SE OF KCLT WILL ALLOW WINDS TO
REMAIN SOLIDLY NW TO N GOING FORWARD. SPEEDS WILL PICK UP WITH
MIXING LATER THIS MORNING...BUT GENERALLY REMAIN 10 KT OR LESS
THROUGH THE DAY...WITH THE GRADIENT RELAXING LATE. LITTLE MORE THAN
FEW TO SCT CIRRUS IS EXPECTED EARLY IN THE PERIOD.

ELSEWHERE...SOLID NW FLOW IS EXPECTED AS THE PASSING COLD FRONT HAS
MOVED THROUGH THE REGION EARLY THIS MORNING. THE GRADIENT WILL
TIGHTEN ACROSS THE MTNS THROUGH DAYBREAK...AND OCCASIONAL WIND GUSTS
TO 18 KT WILL OCCUR AT KAVL THROUGH AT LEAST MID AFTN.
ELSEWHERE...EXPECT NW TO N WINDS AT LESS THAN 10 KT...BECOMING LIGHT
TOWARD EVENING. ANY EARLY PERIOD CIRRUS WILL CLEAR TO THE SE THROUGH
THE DAY.

OUTLOOK...DRY HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH
FRIDAY. A STORM SYSTEM WILL MOVE FROM THE SRN PLAINS TO THE SRN
APPALACHIANS ON 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...

            08-14Z        14-20Z        20-02Z        02-08Z
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...HG
SHORT TERM...CDG
LONG TERM...JOH
AVIATION...HG