Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 141800
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
200 PM 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 150 PM...WEAK SHOWERS CONTINUED ACROSS THE I-85
CORRIDOR...ASSOCIATED WITH SURGING NE WINDS AND ISENTROPIC LIFT.
ISENTROPIC LIFT SHOULD GRADUALLY WEAKEN THROUGH THE REMAINDER OF THE
AFTERNOON HOURS. I WILL UPDATE THE POPS TO LOWER VALUES EAST OF THE
MTNS...PRESERVING VALUES ACROSS THE HIGH TERRAIN. TEMPERATURES
REMAIN ON TRACK...BELOW GUIDANCE.

AS OF 930 AM...THE KGSP RADAR INDICATED A SURGE OF NE FLOW BEHIND A
BOUNDARY CROSSING 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 /18Z SUNDAY THROUGH FRIDAY/...
AT KCLT...THE 12Z NAM INDICATES THAT WEAK LLVL LIFT WILL CONTINUE
ACROSS THE TERMINAL THROUGH MOST OF THE AFTERNOON. HOWEVER...LIFT
WEAKENS CLOSER TO 0Z...I WILL INDICATE PERIODS OF VFR FROM 18-19 AS
A SHOWER PASSES BY...WITH VFR SETTLING IN AROUND 22Z. WEAK LLVL LIFT
WILL LIKELY REDEVELOP LATER TONIGHT. ONCE THE FORCING
DEVELOPS...RESTRICTIVE CEILINGS SHOULD READILY REDEVELOP ACROSS THE
REGION. I WILL INDICATE THE LOWEST CEILINGS FROM 8Z-14Z. THE ARRIVAL
OF SLIGHTLY DRIER AIR MAY ALLOW CLOUD BASES TO LIFT TO 035 BY 14Z.
THROUGH THE TAF PERIOD...WINDS WILL REMAIN BETWEEN 3-6 KTS FROM THE
NE...OR CALM. SHRA ARE MOST LIKELY THIS AFTERNOON.

ELSEWHERE...CONDITIONS WILL REMAIN SIMILAR TO KCLT. HOWEVER...SURGE
OF NE FLOW WILL KEEP KAND AND KAVL RESTRICTED THROUGH MOST OF THE
TAF PERIOD. ROUNDS OF LLVL LIFT WILL TAPER OFF THIS AFTERNOON...BUT
WILL REDEVELOP OVERNIGHT. MVFR CONDITIONS SHOULD REMAIN WIDESPREAD
THROUGH MID MORNING MONDAY. VFR CONDITIONS SHOULD SPREAD ACROSS THE
REGION BETWEEN 13Z-15Z.

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...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       HIGH  94%     HIGH  94%     HIGH  82%     HIGH  91%
KGSP       HIGH  84%     MED   78%     MED   74%     MED   79%
KAVL       HIGH  83%     MED   70%     HIGH  89%     HIGH  85%
KHKY       HIGH  91%     HIGH  95%     MED   77%     HIGH  87%
KGMU       HIGH  84%     HIGH  81%     MED   77%     HIGH  80%
KAND       HIGH  94%     HIGH  87%     HIGH  94%     HIGH  91%

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...NED





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