Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 161905 CCA
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
ISSUED BY NATIONAL WEATHER SERVICE COLUMBIA SC
303 PM EDT TUE SEP 16 2014

.SYNOPSIS...
A WEAK BACK DOOR COLD FRONT WILL SLIDE THROUGH REGION THIS EVENING
WITH ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE ALONG
AND AHEAD OF THE FRONT.  OTHERWISE...HIGH PRESSURE TO THE NORTH
USHERING IN NORTHERLY FLOW ON WEDNESDAY WILL LEAD TO MUCH COOLER AND
DRIER AIR FOR THE REMAINDER OF THE WORK WEEK...LASTING THROUGH THE
WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 240 PM EDT TUESDAY...LATEST SPC MESOANALYSIS INDICATES A
RATHER LARGE AND INCREASINGLY UNSTABLE AIRMASS ACROSS MUCH OF THE
LOWER TERRAIN OF NORTHEAST GA AND THE WESTERN CAROLINAS.  CONVECTION
INITIATING ACROSS THE FOOTHILLS OF THE BLUE RIDGE INTO THE NC
PIEDMONT WILL CONTINUE THROUGH THE AFTERNOON WITH COVERAGE EXPANDING
SOUTHWARD INTO THE UPSTATE OF SC AND NORTHEAST GA.  SOUNDINGS ACROSS
THESE ZONES DO INDICATE DECENT CAPE THROUGH THE LOWEST 400MB WITH
INCREASING SHEAR AHEAD OF AN APPROACHING WEAK UPPER SHORT WAVE.
THUS...AFTERNOON FORECAST FEATURES ISOLATED/SCATTERED POPS WITH A
FEW STRONG THUNDERSTORMS POSSIBLE WITH GUSTY WINDS AND CLOUD TO
GROUND LIGHTNING BEING THE PRIMARY THREATS.  OTHERWISE...ASIDE FOR
POSSIBLE/BRIEF REDEVELOPMENT ALONG BACK DOOR FRONTAL
BOUNDARY...EXPECTING CONVECTION TO ERODE BY LATE EVENING AS HEATING
SUBSIDES AND DRY AIR ADVECTS IN.  GUIDANCE DOES INDICATE THAT THE
BOUNDARY ITSELF WILL BE RATHER SLOW TO PUSH THROUGH THE PIEDMONT
REGIONS OF NC/SC OVERNIGHT LEADING TO CONTINUED CLOUDINESS AND LOW
END PRECIPITATION CHANCES INTO MORNING ALONG AND EAST OF I77.

FOR WEDNESDAY...HIGH PRESSURE SLIDING EAST THROUGH THE OHIO VALLEY
WILL CONTINUE TO DOMINATE THE WEATHER PATTERN LEADING TO PREVAILING
NORTHERLY FLOW AND WELL BELOW NORMAL TEMPERATURES AMIDST MOSTLY
SUNNY SKIES.  FORECAST WILL REMAIN DRY FOR MOST OF THE REGION WITH
ONLY ISOLATED SHOWERS POSSIBLE ACROSS THE EAST WHERE LINGERING
FRONTAL MOISTURE RESIDES...AND ALSO ALONG PORTIONS OF THE WESTERN NC
MOUNTAINS WHERE UPSLOPE FLOW COULD INDUCE A FEW SHOWERS.  NOT
EXPECTING ANY DEEP CONVECTION ON TUESDAY AS DRIER/COOLER BOUNDARY
LAYER WILL INHIBIT INSTABILITY THROUGHOUT THE DAY.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 245 PM TUE...LONG WAVE TROF REMAINS OVER THE ERN CONUS THRU
THE PERIOD...ALTHOUGH THE AXIS DOES MOVE OFF SHORE BY THE END OF
THE PERIOD. A SERIES OF WEAK SHORT WAVES MOVE ACROSS THE AREA THRU
THE TROF. HOWEVER...THERE IS LITTLE DEEP MOISTURE AND FORCING
ASSOCIATED WITH THESE SYSTEMS. THERE IS QUITE A BIT OF LOW LEVEL
MOISTURE AND SOME MECHANICAL FORCING IN THE LOW LEVEL ELY FLOW
WITH SFC HIGH PRESSURE REMAINING RIDGED INTO THE AREA FROM THE
NORTH. HOWEVER...FORECAST SOUNDINGS SHOW THE ATMOS REMAINS CAPPED
THRU THE PERIOD WITH WARM MID LEVEL TEMPS. THEREFORE...HAVE GONE
WITH A DRY FORECAST THRU THE PERIOD...EXCEPT FOR SOME LINGERING
CONVECTION WED EVENING. THERE SHUD BE QUITE A BIT OF NIGHT TIME
CLOUDS WITH THE LOW LEVEL MOISTURE AND ELY FLOW...WITH SOME
CLEARING DURING THE DAY. TEMPS WILL BE AROUND 5 DEGREES BELOW
NORMAL.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 300 PM TUE...UPPER TROF BRIEFLY BUILDS INTO THE AREA EARLY
IN THE MEDIUM RANGE AS AN UPPER TROF MOVES OFF SHORE. ANOTHER
UPPER TROF BUILDS OVER THE ERN CONUS ON MON AND REMAINS ON TUE. AT
THE SFC...HIGH PRESSURE REMAINS RIDGED INTO THE AREA FROM THE
NORTH WITH A MODERATING AIR MASS UNTIL A COLD FRONT CROSSES THE
AREA MONDAY. HIGH PRESSURE BEGINS TO BUILD IN AS THE FRONT SLOWLY
MOVES EAST ON TUE. EXPECT A DRY FCST FRI AND SAT...WITH ONLY A
SLIGHT CHC OF PRECIP MOVING IN ACROSS THE WEST AHEAD OF THE FRONT
ON SUN. MTNS WILL SEE THE BEST CHC OF PRECIP MON WHERE MOISTURE
AND FORCING ARE HIGHEST. PRECIP CHC DIMINISHES TO SLIGHT CHC FOR
TUE AND MAINLY OUTSIDE OF THE MTNS IN THE LINGERING MOISTURE
BEHIND THE SLOW MOVING FRONT. BELOW NORMAL TEMPS RISE TO A LITTLE
ABOVE NORMAL AHEAD OF THE FRONT...THEN DROP A LITTLE BELOW NORMAL
BEHIND THE FRONT ON TUE.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE MAJORITY OF THE
FORECAST CYCLE WITH THE EXCEPTION OF POSSIBLE AFTERNOON TSRA AND
EARLY MORNING VISB/CIG RESTRICTIONS. INITIALIZED TAF WITH LIGHT
NORTHWEST WINDS AND BKN LOW VFR CU WITH A 4HR TEMPO FROM 22-02Z TO
ACCOUNT FOR AFTERNOON CONVECTION IN THE WARM SECTOR AHEAD OF AN
APPROACHING BACK DOOR FRONTAL BOUNDARY. BEYOND THAT...KEPT PROB30
IN THE NEXT FM GROUP AS LATEST CAMS INDICATED POTENTIAL FOR
REDEVELOPMENT AS THE FRONT ITSELF SLIDES THROUGH LATER THIS
EVENING. LATEST NAM RUNS SLOW THE FRONTAL PROGRESSION THROUGH THE
REGION OVERNIGHT LEADING TO PERSISTENT MVFR CIGS/VISB RESTRICTIONS
THROUGH MORNING WITH VISB IMPROVING BY LATE MORNING. KEPT
NORTHERLY WINDS AND MVFR CIGS THROUGH THE REMAINDER OF THE PERIOD
AS SOUNDINGS INDICATE CONTINUED SATURATION IN THE MOIST LOW
LEVELS.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE WITH VFR CONDITIONS
PREVAILING THROUGH THE MAJORITY OF THE FORECAST PERIOD ASIDE FOR
AFTERNOON TSRA AND EARLY MORNING VISB/CIG RESTRICTIONS.
INITIALIZED ALL TAF SITES WITH VCTS MENTION WITH EMBEDDED TEMPO
GROUPS FOR TSRA AND 4SM VISB WITH SLIGHT TIMING DIFFERENCES
DEPENDING ON SITE LOCATION. CONTINUED WITH VCTS MENTION BEYOND
TEMPOS AT ALL SITES EXCEPT FOR KAVL AS THE FRONTAL BOUNDARY SLIDES
SOUTHEAST. FURTHER CIG AND VISB RESTRICTIONS ARE EXPECTED
OVERNIGHT AT ALL SITES...WITH GUIDANCE HITTING THE MOUNTAIN
VALLEYS THE HARDEST DESPITE THE FROPA. THUS...CARRIED MVFR
CIGS/VISB AT KAVL BUT OPTED FOR ONLY A TEMPO FOR IFR CONDITIONS
DUE TO LOW CONFIDENCE. CONDITIONS WILL IMPROVE AFTER DAYBREAK AS
HIGH PRESSURE CONTINUES TO BUILD LEADING TO THE RETURN OF VFR
AT ALL LOCATIONS ASIDE FOR KHKY WHERE LINGERING MOISTURE WILL
ALLOW FOR PERSISTENT MVFR CIGS THROUGH THE PERIOD.

OUTLOOK...ALTHOUGH THE CHANCES FOR DIURNAL CONVECTION WILL GREATLY
DIMINISH AFTER WEDNESDAY...THE POTENTIAL FOR LATE NIGHT/MORNING
FOG/STRATUS WILL PERSIST INTO LATE WEEK...ESP IN THE MTN VALLEYS.
CONDITIONS MAY FINALLY DRY OUT FOR THE WEEKEND.

CONFIDENCE TABLE...

            12-18Z        18-24Z        00-06Z        06-12Z
KCLT       MED   67%     HIGH 100%     HIGH 100%     HIGH 100%
KGSP       MED   67%     HIGH 100%     HIGH 100%     HIGH 100%
KAVL       HIGH  86%     HIGH 100%     MED   78%     HIGH  96%
KHKY       LOW   59%     HIGH 100%     HIGH 100%     HIGH  91%
KGMU       MED   79%     HIGH 100%     HIGH 100%     HIGH  95%
KAND       HIGH  82%     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...CDG
NEAR TERM...CDG
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...CDG





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