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000
FXUS62 KGSP 310743
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
343 AM EDT THU JUL 31 2014

.SYNOPSIS...
RIDGE OF CANADIAN HIGH PRESSURE REMAINS OVER THE AREA INTO THE
WEEKEND AS A FRONTAL SYSTEM MOVES NORTH TO THE COAST. MOISTURE
INCREASES BETWEEN THESE TWO SYSTEMS INCREASING THE CHANCES OF
WIDESPREAD SHOWERS AND THUNDERSTORMS. CONDITIONS RETURN TO THOSE
MORE TYPICAL OF LATE SUMMER BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 300 AM EDT THURSDAY...UPPER TROF LOCATED OVER THE EASTERN
UNITED STATES WILL REMAIN IN PLACE WHILE A SHORT WAVE IMPULSE PASSES
THROUGH THE MEAN FLOW.  CURRENTLY...SAID SHORT WAVE IS LOCATED
ACROSS THE CENTRAL PLAINS...PUSHING EAST INTO THE MIDSOUTH.
CONSEQUENT CIRRUS SHIELD CONTINUES TO ADVECT DOWNSTREAM ACROSS THE
SOUTHERN APPS LEADING TO PARTLY/MOSTLY CLOUDY SKIES THIS MORNING.

MEANWHILE...SURFACE WARM FRONT CONTINUES TO SPREAD NORTHWEST ACROSS
THE MIDLANDS OF SC...SPILLING INTO THE FORECAST AREA BY MID/LATE
MORNING LEADING TO INCREASING LOW LEVEL CLOUDINESS.  A CONVERGENCE
AXIS ALONG THE LEADING EDGE OF THIS INTRUDING WARM FRONT...AND WEAK
WEDGE LIKE SURFACE RIDGE WILL CONTINUE TO PROMOTE WEAK SHOWER
ACTIVITY EARLY IN THE DAY.  PRECIPITATION CHANCES WILL INCREASE
THROUGH THE DAY HOWEVER AS MODERATE UPGLIDE ATOP WEDGE BOUNDARY
COMBINES WITH WEAK ELEVATED INSTABILITY TO SUPPORT CONVECTION.

FORECAST WILL INITIATE THIS MORNING WITH SLIGHT CHANCE POPS ACROSS
THE UPSTATE...NORTHEAST GA...AND THE NC FOOTHILLS/PIEDMONT...WITH
POPS INCREASING TO LOW END LIKELY LEVELS NEAR THE END OF THE
PERIOD.  AS FOR THE MOUNTAINS...ABOVE MENTION UPGLIDE/INSTABILITY
WILL BE ENHANCED AS WEAK EASTERLY UPSLOPE FLOW COMMENCES LEADING TO
HIGHER POPS ACROSS THE TERRAIN.  FOR THE MOUNTAINS...FORECAST WILL
FEATURE CHANCE LEVEL POPS INITIALLY WITH CATEGORICAL POPS TO ROUND
OUT THE FORECAST.  DUE TO RETURN FLOW OF MOISTURE THERE WILL BE SOME
ELEVATED INSTABILITY ACROSS THE REGION TODAY PER FORECAST
SOUNDINGS.  THEREFORE CANNOT RULE OUT AN ISOLATED THUNDERSTORM WITH
A PRIMARY THREAT OF CLOUD TO GROUND LIGHTING ESPECIALLY WHEN ABOVE
MENTIONED SHORT WAVE ENERGY MOVES IN LATE.  SPEAKING
OF...PRECIPITATION RATES WILL ALSO IMPROVE LATE TONIGHT INTO THE
OVERNIGHT WITH THE HIGHEST AMOUNTS RESIDING ALONG THE BLUE RIDGE
WHERE UPWARDS OF 1 TO 1.5 INCHES IS POSSIBLE.  TEMPERATURES THROUGH
THE PERIOD WILL REMAIN 8-10 DEGREES BELOW NORMAL AS RADIATIONAL
HEATING IS LIMITED DUE TO ABUNDANT SKY COVER AND PRECIPITATION.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
AS OF 330 AM...IT IS LOOKING MORE AND MORE LIKELY THAT THE FIRST
PART OF THE WEEKEND WILL BE WET. SWLY UPPER FLOW INCREASES THRU THE
PERIOD AS A TROF AXIS TO THE WEST SHARPENS AND THE ATLANTIC
SUB-TROPICAL ANTI-CYCLONE MOVES WEST TOWARD THE COAST. SHORT WAVES
MOVE THRU THE FLOW AND ACROSS THE AREA KEEPING Q-VECTOR CONVERGENCE
IN PLACE. IN ADDITION...UPPER LEVEL DIVERGENCE REMAINS OVER THE AREA
AS THE RIGHT ENTRANCE REGION OF AN UPPER JET BECOMES PARKED NEARBY.
A SERIES OF H85 LOWS MOVE OVER THE AREA BRINGING PERIODS OF SELY LOW
LEVEL FLOW. THESE KEEP LOW LEVEL AND DEEP MOISTURE ACROSS THE AREA
AS WELL. BEST POP WILL BE ALONG THE BLUE RIDGE WHERE UPSLOPE FLOW
MAXIMIZES. HOWEVER...LIKELY POP WILL BE FEATURED ALL AREAS GIVEN THE
MOISTURE AND FORCING. SCT TSRA SHUD ALSO DEVELOP...MAINLY ALONG AND
SOUTH OF I-85 AS ELEVATED INSTABILITY DEVELOPS. FCST HODOGRAPHS SHOW
QUITE A BIT OF SPEED AND DIRECTIONAL SHEAR DEVELOPS. RIGHT NOW...
INSTABILITY REMAINS RELATIVELY WEAK AND ELEVATED...BUT WILL HAVE TO
KEEP AN EYE ON THIS.

SATURDAY WILL BE SIMILAR TO FRIDAY EXCEPT FOR THE WEAKENING SFC
RIDGE LEADING TO INCREASED INSTABILITY AND BETTER CHC OF SCT TSRA
ACROSS THE AREA. ALTHOUGH INSTABILITY WILL BE GREATER...SHEAR WILL
BE MUCH LESS. STILL TOO EARLY TO TELL IF AREAS OF HEAVY RAIN WILL
DEVELOP EITHER DAY...BUT IT CANNOT BE RULED OUT. HIGHS FRIDAY WILL
BE 10 TO 15 DEGREES BELOW NORMAL...THEN RISE ABOUT 5 DEGREES ON SAT.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 340 AM...THE NRN PART OF THE UPPER TROF SLIDES EAST OF THE
AREA LEAVING A WEAK UPPER LOW OVER THE SERN US. THE UPPER LOW THEN
SLIDES ACROSS THE AREA LEAVING ZONAL FLOW IN PLACE. AT THE SFC... A
WEAK FRONT OR BAROCLINIC BOUNDARY REMAINS ALONG THE COAST WITH WEAK
HIGH PRESSURE OVER THE APPALACHIANS. LIKELY POP ON SUN DROPS TO
DIURNAL CHC POP FOR THE REST OF THE PERIOD. HIGHS SUN AROUND 10
DEGREES BELOW NORMAL SLOWLY RISE TO NEAR NORMAL BY THE END OF THE
PERIOD.

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
AT KCLT...A MIXTURE OF VFR/MVFR CONDITIONS WILL PREVAIL THROUGH THIS
TAF PERIOD.  INITIALIZED TAF WITH BKN LOW/MID LEVEL CIG WHICH
CARRIES THROUGH 14Z.  AT THAT TIME...EXPECTING MOISTURE ADVECTION
FROM THE EAST TO SPREAD AN MVFR STRATUS LAYER OVER THE
REGION...LASTING THROUGH AROUND NOON WHERE LOW VFR STRATUS WILL
PREVAIL.  MARGINAL UPGLIDE COMBINED WITH WEAK INSTABILITY COULD
PRODUCE SHRA/TSRA AT THE AIRFIELD LATE IN THE PERIOD...THEREFORE
OPTED FOR PROB30 FOR TSRA AT 00Z WHERE CIGS ALSO LOWER BACK TO MVFR
LEVELS.  EXPECTING CIGS TO RECOVER AS PRECIP SUBSIDES NEAR THE END
OF THE TAF CYCLE WITH LOW VFR PREVAILING YET AGAIN.  WINDS THROUGH
THE PERIOD WILL BE A LITTLE TRICKY.  INITIALIZED WINDS AT CALM
BEFORE INCREASING SOUTHEASTERLY FLOW DOMINATES THROUGH MUCH OF THE
DAY.  LATE IN THE AFTERNOON TO EARLY EVENING...EXPECTING WINDS TO
BACK NORTHEASTERLY SOMEWHAT AS HIGH PRESSURE WEDGES IN.

ELSEWHERE...A MIXTURE OF VFR/MVFR CONDITIONS WILL PREVAIL AT ALL
SITES THROUGH THE PERIOD WITH KAVL ACTUALLY LOWERING TO IFR LEVELS
LATE IN THE PERIOD.  LOW/MID VFR CIGS WILL LOWER TO MVFR LEVELS
AROUND DAYBREAK AS MOISTURE ADVECTS IN FROM THE EAST.  THESE CIGS
WILL LIKELY CARRY THROUGH THE MID/LATE MORNING HOURS BEFORE LIFTING
TO LOW VFR.  MODELS HAVE SOME DISAGREEMENT REGARDING PRECIP THIS
MORNING AT THE SC SITES...THUS DUE TO LOW CONFIDENCE KEPT OUT OF
TAF.  THAT SAID...LATER IN THE DAY MODELS DO AGREE ON POTENTIAL FOR
SCT SHRA/TSRA AT ALL SITES.  THUS...VCSH/VCTS MENTION IS CARRIED AT
ALL LOCATIONS WITH KAVL ACTUALLY PREVAILING -SHRA DURING THE
AFTERNOON WHERE UPGLIDE/UPSLOPE/INSTABILITY WILL BE GREATEST ALONG
THE TERRAIN.  EXPECTING CIGS TO LOWER BACK TO MVFR LEVELS AS PRECIP
COMMENCES AT EACH LOCATION...AND REMAIN THERE DUE TO SUBSTANTIAL
MOISTURE IN THE BOUNDARY LAYER.  ALSO INCLUDED IFR CIGS AT KAVL LATE
IN THE PERIOD AS GUIDANCE IS IN AGREEMENT REGARDING LOW STRATUS
DEVELOPMENT ALONG THE HIGH TERRAIN OVERNIGHT.  WINDS THROUGH THE
PERIOD WILL REMAIN LIGHT AND SOUTHERLY AT KAVL...AND EAST
NORTHEASTERLY ELSEWHERE.

OUTLOOK...MOISTURE WILL CONTINUE TO INCREASE THROUGH THE
REMAINDER OF THE WORK WEEK AS A WARM FRONT APPROACHES FROM THE EAST
AND SOUTHEASTERLY FLOW CONTINUES. UNSETTLED WEATHER WITH ENHANCED
PRECIPITATION CHANCES ALONG WITH MORNING FOG/STRATUS ARE EXPECTED
THROUGH THE WEEKEND.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-07Z
KCLT       HIGH 100%     MED   72%     HIGH  86%     HIGH  80%
KGSP       HIGH  87%     MED   75%     HIGH  87%     HIGH  80%
KAVL       HIGH  87%     MED   67%     MED   78%     HIGH  80%
KHKY       HIGH  86%     HIGH  92%     HIGH  89%     MED   76%
KGMU       HIGH  89%     MED   75%     HIGH  84%     MED   76%
KAND       MED   75%     MED   78%     HIGH  88%     MED   78%

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...RWH
NEAR TERM...CDG
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG