Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 141338
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
938 AM EDT SUN SEP 14 2014

.SYNOPSIS...
COOL BUT UNSETTLED WEATHER WILL CONTINUE THROUGH MONDAY NIGHT...AS A
STATIONARY FRONT WILL REMAIN JUST TO OUR SOUTH BEFORE AN UPPER
DISTURBANCE PASSES THROUGH. A COLD FRONT WILL THEN CROSS THE AREA IN
ITS WAKE...WHICH AGAIN STALLS TO OUR SOUTH. THIS WILL KEEP
TEMPERATURES A FEW DEGREES BELOW NORMAL INTO NEXT WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 930 AM...THE KGSP RADAR INDICATED A SURGE OF NE FLOW BEHIND A
BOUNDARY SLIDING SW ACROSS THE GREENVILLE/SPARTANBURG COUNTIES.
THE REGION AHEAD OF THIS BOUNDARY WILL LIKELY SEE AN INCREASE IN
LOW CLOUDS AND LIGHT RAIN AND DRIZZLE...WITH STEADY TEMPS. AREAS
NORTH...SHOULD SEE LESS RAINFALL COVERAGE AND HIGHER CLOUD
BASES...TEMPS SLOWLY WARMING. I WILL UPDATE THE FORECAST TO
ACCOUNT FOR THESE EXPECTED TRENDS.

AS OF 645 AM EDT...HIGH PRESSURE WILL BUILD OUT OF THE ERN GREAT
LAKES TOWARD THE MID-ATLANTIC COAST TODAY...REINFORCING WEDGE-LIKE
RIDGING ALREADY IN PLACE ACRS THE WRN CAROLINAS. WEDGE FRONT APPEARS
TO BE JUST SOUTH OF I-20 AS DELINEATED BY WINDS AND DEWPOINTS.

STILL SEEING SCT LIGHT SHOWERS MAINLY OVER THE I-85 CORRIDOR.
INTERESTINGLY THIS IS RIGHT WHERE THE 06Z NAM 300K SFC SHOWS THE
BEST UPGLIDE AT 12Z. GOING FWD IN TIME TO 15Z THE WINDS VEER AND THE
SETUP DIMINISHES. HOWEVER AS DIURNAL HEATING GETS UNDERWAY ALONG THE
PERIPHERY OF THE WEDGE...THIS WILL TAKE OVER AS THE PRIMARY DRIVER
FOR POPS. THE NAM/GFS AND MESO MODELS DEVELOP SOME LIGHT QPF OVER
THE CENT/SRN MTNS AND MUCH OF THE SC/GA ZONES AS A RESULT. HAVE
SOLID CHC SHRA MENTION TODAY IN THESE AREAS...AND SCHC RA IN THE
AREAS ONLY UNDER THE INFLUENCE OF THE UPGLIDE. THE VERY HIGH PWAT
VALUES WE SAW FRI-SAT HAVE NOW RETREATED SOUTH OF THE WEDGE SO HEAVY
RAIN IS OF MUCH LESS CONCERN TODAY. SKIES ARE EXPECTED TO REMAIN
VIRTUALLY OVERCAST OVER THE WEDGE...AND THE AIRMASS IS COOLER TO
BEGIN WITH. THUS I WILL CONTINUE TO ADVERTISE MAX TEMPS AROUND 10
DEG BELOW CLIMO. OF COURSE...IF BREAKS ARE ABLE TO FORM AWAY FROM
THE AREAS SEEING PRECIP...THE TEMP FCST COULD QUICKLY BUST.

THOUGH CONFLUENCE IS MINIMAL ALOFT THE SFC HIGH OVER THE
MID-ATLANTIC HOLDS STRONG TONIGHT SO THE WEDGE AND WEAK UPGLIDE
SHOULD REMAIN IN PLACE. HAVE ALLOWED POPS TO DROP OFF AFTER PEAK
HEATING ALONG ITS FRINGE...BUT WILL KEEP SCHC POPS EVERYWHERE THRU
THE NIGHT. THE CLOUD LAYER ATOP THE WEDGE DOES BECOME MORE SHALLOW
PER PROG SOUNDINGS BUT VERY LIGHT PRECIP IS STILL PLAUSIBLE. MIN
TEMPS WILL BE A COUPLE DEGREES ABOVE CLIMO.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 315 AM SUNDAY...AFTER SOMEWHAT OF A LULL IN THE ACTIVE
CONVECTIVE PATTERN DURING THE NEAR TERM...THE LIKELY EROSION OF COLD
AIR DAMMING ON MONDAY SHOULD RESULT IN BETTER INSOLATION AND
DESTABILIZATION ON MONDAY...WHILE MOISTURE SHOULD REMAIN ABUNDANT...
ESP IN THE LOWER LEVELS. ADDITIONALLY...THE SHORT TERM MODELS SEEM
TO BE PICKING UP ON A FAST MOVING UPPER AIR DISTURBANCE EJECTING
FROM THE SOUTHERN PLAINS...AND TAKING AIM ON THE SOUTHEAST BY THE
END OF MONDAY. POPS WILL RANGE FROM 30-50 PERCENT MON AFTERNOON/
EVENING...WITH THE HIGHEST CHANCES FAVORED ACROSS AREAS THAT ARE
MOST LIKELY TO SEE THE MOST ROBUST INSTABILITY (I.E. THE SOUTHWEST
ZONES). WHILE A DIMINISHING TREND IN POPS WILL BE FEATURED MON
NIGHT...THEY WILL GENERALLY REMAIN ABOVE CLIMO...AS A CONSENSUS OF
MODEL GUIDANCE WOULD BRING THE NEXT FRONTAL ZONE INTO THE AREA BY
EARLY TUESDAY.

FOR TUESDAY...A DIURNAL INCREASE IN POP WILL BE ADVERTISED.
HOWEVER...DRIER AIR MAY BEGIN FILTERING INTO THE AREA BY AFTERNOON
IN THE WAKE OF THE AFOREMENTIONED FRONT...ESP ACROSS THE NORTHERN
AND WESTERN ZONES. THEREFORE...POPS WILL BE FEATURED ONLY IN THE
20-30 PERCENT RANGE...RAPIDLY DIMINISHING DURING THE EVENING. TEMPS
WILL GENERALLY REMAIN SLIGHTLY BELOW CLIMO THROUGH THE PERIOD.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 325 AM SUNDAY...THE EARLY PART OF THE MEDIUM RANGE WILL
FEATURE THE NEXT IN A SERIES OF COLD AIR DAMMING EVENTS...AS 1020 MB
SURFACE HIGH OOZES INTO THE MID-ATLANTIC. THIS WILL FAVOR TEMPS
ABOUT 5-10 DEGREES BELOW NORMAL WED/THU. ALTHOUGH CHANCES FOR PRECIP
WILL NOT BE 0 DURING THIS TIME...THERE IS SOME INDICATION IN THE
GLOBAL MODELS THAT NE FLOW WILL ALLOW ENOUGH STABLE AIR TO PENETRATE
INTO THE AREA TO PRECLUDE ANYTHING HIGHER THAN 20/30 POPS DURING
THIS TIME. BY THE END OF THE WEEK...IT APPEARS LIKELY THAT THE WEDGE
WILL BE REINFORCED BY STOUT CANADIAN HIGH PRESSURE MOVING INTO NEW
ENGLAND. THE ATTENDANT SURFACE RIDGE MAY BE STRONG ENOUGH TO SCOUR
THE LINGERING MOISTURE AND FINALLY BRING A PERIOD OF TYPICALLY DRY
EARLY AUTUMN WEATHER TO THE REGION. HOWEVER...THIS IS FAR FROM A
CERTAINTY...AND TOKEN SLIGHT CHANCE POPS WILL BE RETAINED THROUGH
THE END OF THE PERIOD...ALONG WITH BELOW NORMAL TEMPS.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
AT KCLT...WARM UPGLIDE REGIME WILL CONTINUE TODAY ATOP A COOL WEDGE
OF HIGH PRESSURE. MVFR CIG PERSISTS UNTIL LIFTING TO VFR AROUND
MIDDAY. THE WEDGE FRONT WILL BE S OF THE FIELD DURING THE DAY TODAY
AND IS PROGGED TO FOCUS CONVECTIVE DEVELOPMENT... ALBEIT MINOR IN
IMPACT DUE TO POOR LAPSE RATES. ONLY INCLUDED VCSH DUE TO LOW IMPACT
AND COVERAGE OF SHOWERS. NE WINDS CONTINUE UNTIL GOING CALM AFTER
SUNSET. THOUGH UPGLIDE TONIGHT IS QUITE WEAK...THE WEDGE IS UNLIKELY
TO RETREAT AND MODEL PROGS OF MVFR CIGS ARE BELIEVABLE. WITH THE
CALM WINDS AND VERY MOIST CONDITIONS SOME LIGHT FOG IS LIKELY ALSO.

ELSEWHERE...MVFR CIGS ARE THE MAIN CONCERN THIS MRNG WITH HIGH
PRESSURE WEDGE ALLOWING WARM UPGLIDE AND ASSOCIATED CLOUD COVER.
PRECIP CHANCES ARE LOW ENOUGH TO INCLUDE ONLY AS VCSH TODAY...WITH
MOST GUIDANCE SHOWING THE ONGOING WARM UPGLIDE PRODUCING LITTLE
PRECIP. WEAK CONVECTIVE CELLS DEVELOPING NEAR THE WEDGE BOUNDARY ARE
MORE LIKELY THOUGH KAND IS THE ONLY SITE WITH A GOOD SHOT AT SEEING
EFFECTS FROM THESE. WINDS REMAIN NE...EXCEPT AT KAVL WHICH SHOULD
SEE CHANNELED SE FLOW DURING THE AFTN. MOST AREAS SHOULD GO CALM
THIS EVENING. RESTRICTIVE CIGS WILL REDEVELOP EXCEPT AT KHKY...ALONG
WITH MORE FOG THAN SEEN THIS MRNG DUE TO THE SIMILARLY MOIST
CONDITIONS BUT LACK OF WIND.

OUTLOOK...THE WEDGE SHOULD MIX OUT ON MONDAY...BUT SCT
SHOWERS/THUNDERSTORMS WILL DEVELOP AHEAD OF AN APPROACHING COLD
FRONT MONDAY AFTERNOON INTO MONDAY NIGHT. A RETURN TO MAINLY VFR
CONDITIONS IS EXPECTED TUE INTO MIDWEEK OUTSIDE OF RESTRICTIONS WITH
DIURNAL CONVECTION.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-13Z
KCLT       MED   67%     HIGH  93%     HIGH  89%     MED   79%
KGSP       HIGH  92%     HIGH  82%     HIGH  85%     HIGH  89%
KAVL       HIGH  83%     HIGH  84%     HIGH  87%     HIGH  81%
KHKY       MED   72%     HIGH  95%     HIGH  92%     MED   79%
KGMU       HIGH  92%     HIGH  83%     HIGH  87%     HIGH  87%
KAND       HIGH 100%     HIGH  85%     HIGH  85%     HIGH  88%

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...WIMBERLEY
NEAR TERM...NED/WIMBERLEY
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...WIMBERLEY





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