Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 200251
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1051 PM EDT FRI SEP 19 2014

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE WILL LINGER ATOP THE REGION THROUGH
SATURDAY. IN RESPONSE...TEMPERATURES WILL MODERATE OVER THE WEEKEND
AND THEN BEGIN TO DROP AGAIN EARLY NEXT WEEK AS A COLD FRONT MOVES
OVER THE CAROLINAS. COOL AND DRY HIGH PRESSURE WILL SPREAD ACROSS
THE REGION IN THE FRONTS WAKE AND LINGER THROUGH MID WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 1030 PM...NOT MUCH HAPPENING ACROSS THE WRN CAROLINAS. TEMP
TREND IS IN GOOD SHAPE. COULD STILL BE A FEW SHOWERS NEAR THE BLUE
RIDGE...SO NO CHANGES WERE MADE.

REMAINDER OF PREVIOUS DISCUSSION...

COVERAGE SHUD DIMINISH RELATIVELY QUICKLY OUTSIDE OF THE UPSLOPE
AREAS EARLY THIS EVENING...BUT SHRA WILL LINGER ALONG THE BLUE RIDGE
FOR MUCH OF THE NITE. QPF SHUD GENERALLY BE LIGHT UNLESS STORMS CAN
FORM AND BECOME ANCHORED ALONG THE TERRAIN. SHUD BE ANOTHER NITE OF
DEVELOPING LOW CLOUDS...WITH PATCHY FOG. COULD BE PATCHY DENSE FOG
IN THE MTN VALLEYS. LOWS SHUD BE NEAR TO A LITTLE ABOVE NORMAL.

SFC HIGH PRESSURE REMAINS RIDGED INTO THE AREA FROM THE NE SAT...BUT
THE RIDGE WEAKENS AS THE CENTER OF THE HIGH MOVES OFF THE NEW
ENGLAND COAST. LOW PRESSURE DEVELOPS OFF THE SERN COAST AND MOVES NE
THRU THE DAY. AS A RESULT...THE LOW LEVEL FLOW TURNS MORE NELY THRU
THE DAY BRINGING IN DRIER AIR AND AN END TO THE UPSLOPE FLOW.
THEREFORE...EXPECT THE LOW CLOUDS TO SCATTER OUT A LITTLE EARLIER
THAN THE PAST FEW DAYS. WITH LESS LOW LEVEL MOISTURE AND WARMER MID
LEVEL TEMPS...THE ATMOS SHUD REMAIN CAPPED KEEPING THE FCST DRY.
HIGHS WILL BE NEAR OR SLIGHTLY ABOVE NORMAL.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 130 PM EDT FRIDAY...THE PRIMARY HIGHLIGHT OF THE SHORT TERM
FORECAST PERIOD WILL BE A COLD FRONTAL PASSAGE SUNDAY NIGHT INTO
EARLY MONDAY AFTERNOON.  THE FORECAST WILL INITIALIZE DRY SATURDAY
EVENING WITH THE UPPER PATTERN FEATURING A RATHER PROGRESSIVE
POSITIVELY TILTED TROF EJECTING OUT OF THE UPPER MIDWEST.  AT THE
SURFACE...AN ASSOCIATED COLD FRONT WILL STRETCH ALONG THE PARENT
SURFACE TROF FROM LAKE MICHIGAN SOUTHWEST INTO CENTRAL
MISSOURI/NEBRASKA.  MEANWHILE ACROSS THE SOUTHEAST...MODELS CONTINUE
TO INDICATE A WEAK SURFACE DISTURBANCE OFF THE CAROLINA COASTLINE
WHILE SURFACE HIGH PRESSURE CENTERED OVER THE NORTHEAST BEGINS
RETREATING OUT TO SEA.  IN RESPONSE...SOUTHERLY WAA REGIME WILL
RESUME ON SUNDAY AHEAD OF THE ABOVE MENTIONED TROF/FRONT COMPLEX.
THAT SAID...MODELS REMAIN RATHER UNIMPRESSIVE REGARDING THE
MAGNITUDE OF MOISTURE FLUX INTO NORTHEAST GA AND THE WESTERN
CAROLINAS ON SUNDAY BEFORE THE FRONT SWEEPS IN.  SURFACE DEWPOINTS
WILL STRUGGLE TO TOP THE 60 DEGREE MARK LEADING TO MINIMAL MOISTURE
AVAILABILITY FOR BOTH PREFRONTAL CONVECTION IN THE QUASI WARM
SECTOR...AND ALSO FOR FRONTAL CONVECTION DURING THE NOCTURNAL
FROPA.  AS A RESULT...SOUNDINGS REMAIN SOMEWHAT STABLE DUE TO BOTH
LACK OF LOW LEVEL MOISTURE AND WARM MID LEVEL TEMPERATURES
EFFECTIVELY KEEPING CONVECTION AT BAY.  ALL THAT SAID...SHEAR WILL
BE INCREASING AS THE UPPER JET DYNAMICS AND ASSOCIATED VORTICITY
MAXIMA PASS THROUGH THE OHIO VALLEY THEREFORE A ROGUE STRONG/SEVERE
THUNDERSTORM CANNOT BE RULED OUT AT THIS TIME...ESPECIALLY NORTH OF
I40 WHERE BETTER DYNAMICS ARE IN PLAY.

CONVECTION WILL ERODE WITH HEATING LOSS AS THE FRONT SPILLS INTO THE
HIGH TERRAIN SUNDAY NIGHT...EVENTUALLY SLIDING INTO THE SOUTHERN NC
PIEDMONT...NORTHEAST GA...AND SC UPSTATE BY LATE MORNING TO EARLY
AFTERNOON MONDAY BEFORE ANY HEATING CAN SUBSTANTIALLY DESTABILIZE
THE ATMOSPHERE.  THUS...NO ROBUST CONVECTION IS EXPECTED MONDAY
ALONG THE BOUNDARY AS IT SLIDES SOUTH THROUGH THE CWFA.  HIGH
PRESSURE WILL ADVECT INTO THE REGION QUICKLY BEHIND THE FRONT LIKELY
LEADING TO THE FIRST ROUND OF FALL LIKE WEATHER THROUGH THE
PERIOD.   THEREFORE THE FORECAST WILL FEATURE CHANCE LEVEL POPS
ACROSS THE HIGH TERRAIN ON SUNDAY EVENING WITH ONLY SLIGHT CHANCE
POPS HIGHLIGHTED OVERNIGHT ACROSS NORTHEAST GA AND THE NC/SC
PIEDMONT.  SLIGHT CHANCE POPS WILL ONCE AGAIN BE FEATURED EARLY ON
MONDAY ALONG AND SOUTH OF THE I85 CORRIDOR ASSOCIATED WITH THE
PASSING BOUNDARY WITH A DRY FORECAST PREVAILING ELSEWHERE.
TEMPERATURES WILL REMAIN AT OR ABOVE NORMAL LEVELS FOR SUNDAY AHEAD
OF THE FRONT BEFORE COOLING ON MONDAY TO BELOW NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 2 PM FRIDAY...THE MEDIUM RANGE FCST PICKS UP AT 00Z ON TUESDAY
WITH THE LONGWAVE UPPER TROF LIFTING NE OF THE REGION AND HEIGHTS
BEGINNING TO RISE. OVER THE NEXT COUPLE OF DAYS...A VERY BROAD UPPER
RIDGE WILL THEN SPREAD ACROSS THE MAJORITY OF THE CONUS AND REMAIN
IN PLACE THRU NEW DAY 7. AT THE SFC...A STRONG CANADIAN HIGH WILL
SPREAD ACROSS THE REGION ON TUES BRINGING MUCH COOLER AND DRIER AIR
TO THE CAROLINAS. OVER THE NEXT COUPLE OF DAYS...AS THIS HIGH DRIFTS
EASTWARD ANOTHER REINFORCING ONTARIO HIGH WILL SLIDE SE AND MERGE
WITH THE ORIGINAL HIGH. THIS WILL CREATE A STRONGER HIGH CENTERED
OVER NEW ENGLAND AND SET OUR AREA UP FOR ANOTHER COOL AIR WEDGE
PATTERN. THE LONG RANGE MODELS INDICATE THAT THE WEDGE WILL LIKELY
REMAIN IN PLACE THRU THE END OF THE PERIOD ON FRI...WITH SOME DEEPER
LYR MOISTURE ENCROACHING UPON THE CWFA FROM THE SOUTH AND EAST LATE
THURS AND INTO FRI. AS FOR THE SENSIBLE FCST...WE CAN EXPECT COOL
AND DRY CONDITIONS THRU AT LEAST WED WITH ONLY SLIGHT CHANCE POPS
COMING INTO THE PICTURE DURING THE LATTER PART OF THURS AND
LINGERING THRU FRI. TEMPS SHOULD START OUT JUST BELOW CLIMATOLOGY ON
TUES AND DROP A FEW MORE DEGREES THRU THE PERIOD WITH HIGHS IN THE
LOW TO MID 70S OVER THE LOWER ELEVATIONS AND MID TO UPPER 60S OVER
THE HIGHER TERRAIN.

&&

.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
AT KCLT...ONLY SCATTERED MID LEVEL CLOUDS REMAIN AT 00Z...BUT
SATELLITE IMAGERY SHOWS THE DIMINISHING TREND CONTINUING. WIND WILL
BE NE THROUGH THE EVENING HOURS. WHAT IS INTERESTING IS THE MODEL
GUIDANCE TREND. IN SPITE OF THE CONTINUED EASTERLY FLOW AT LOW
LEVELS...THE NEW GUIDANCE FAILS TO DEVELOP ANY CEILING RESTRICTION
DURING THE PRE-DAWN HOURS ON SATURDAY MORNING...ON ACCOUNT OF A
PATCH OF DRIER AIR IN THE 2K-6K FT LAYER THAT MOVES IN FROM THE EAST
AROUND DAYBREAK. THE NEW TAF FOLLOWS THAT TREND OF DRYING FROM THE
EAST AND OPTIMISTICALLY REMAINS VFR...BUT WE SHOULD NOTE THAT MVFR
LEVEL CLOUDS ARE NOT OUT OF THE QUESTION AS THERE WILL PROBABLY BE A
LOW CLOUD DECK ACROSS THE SC MIDLANDS. GOING WITH THE DRIER
SCENARIO...THE CLOUDS SHOULD SCATTER OUT BY MID MORNING. WIND WILL
REMAIN GENERALLY NE.

ELSEWHERE...THE DRY AIR DOES NOT MAKE IT FAR ENOUGH WEST BY SUNRISE
SATURDAY TO PREVENT A LOW CLOUD DECK FROM DEVELOPING IN THE UPSLOPE
AREAS NEAR THE BLUE RIDGE. MOST OF THE TAF SITES EVENTUALLY DEVELOP
AN MVFR CEILING IN THE 07Z TO 10Z TIME FRAME. CONFIDENCE HIGH ENOUGH
TO TAKE THE CEILING/VIS DOWN TO IFR AT KAVL BY 08Z...BUT THIS COULD
HAPPEN EARLIER THAN THAT. THE CEILING SHOULD LIFT TO VFR AROUND
14Z...THEN SCATTER OUT AT MIDDAY AS DRY AIR WORKS IN FROM THE EAST.
EXPECT WIND TO REMAIN GENERALLY FROM THE NE.

OUTLOOK...CONDITIONS SHOULD REMAIN GENERALLY VFR FOR THE LATTER PART
OF THE WEEKEND...BUT WITH MOUNTAIN VALLEY FOG NEAR KAVL IN THE EARLY
MORNING HOURS. A COLD FRONT WILL BRING A CHANCE FOR RESTRICTIONS
MAINLY OVER THE MTNS SUNDAY NIGHT AND MONDAY MORNING. HIGH PRESSURE
BUILDS BACK IN EARLY NEXT WEEK.

CONFIDENCE TABLE...

            03-09Z        09-15Z        15-21Z        21-03Z
KCLT       HIGH 100%     MED   78%     HIGH 100%     HIGH 100%
KGSP       HIGH  98%     MED   75%     HIGH 100%     HIGH 100%
KAVL       MED   77%     MED   66%     HIGH 100%     HIGH 100%
KHKY       HIGH 100%     MED   77%     HIGH 100%     HIGH 100%
KGMU       HIGH 100%     MED   75%     HIGH 100%     HIGH 100%
KAND       HIGH  85%     MED   73%     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...JPT
NEAR TERM...PM/RWH
SHORT TERM...CDG
LONG TERM...JPT
AVIATION...PM/RWH






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