Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 190137
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
937 PM EDT THU SEP 18 2014

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE WILL LINGER ATOP THE REGION INTO
SATURDAY. COOL TEMPERATURES WILL RETURN TO NORMAL READINGS ON SUNDAY
AHEAD OF A COLD FRONT WHICH IS FORECAST TO PASS THROUGH ON MONDAY.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 930 PM...KGSP RADAR CONTINUES TO SHOW SOME SHOWER ACTIVITY
ACROSS THE FCST AREA...WITH THE BEST COVERAGE ALONG THE EASTERN
FRINGE OF THE CLT METRO AREA. WILL BUMP THE PRECIP PROBABILITY UP TO
THE CHANCE RANGE TO ACCOUNT FOR THE TREND. TEMPS ARE IN GOOD SHAPE.

REMAINDER OF PREVIOUS DISCUSSION...

HIGH PRESSURE CONTINUES TO BUILD INTO THE AREA FROM THE NORTH
OVERNIGHT. THIS WILL LEAD TO AN INCREASE LOW LEVEL ELY TO SELY FLOW.
COPIOUS LOW LEVEL MOISTURE WILL REMAIN ACROSS THE AREA AS WELL.
THEREFORE...EXPECT A RETURN OF LOW CLOUDS ACROSS THE AREA. ALTHOUGH
OVERALL PRECIP COVERAGE WILL DECREASE AFTER MIDNIGHT...THE INCREASED
UPSLOPE FLOW AND WEAK ISENTROPIC LIFT...WILL KEEP AT LEAST ISOLATED
SHRA ALONG THE BLUE RIDGE...ALONG WITH PATCHY DRIZZLE ACROSS MUCH OF
THE AREA. PATCHY FOG...WITH ISOLATED DENSE FOG...WILL DEVELOP AGAIN
AS WELL. LOWS WILL BE A LITTLE ABOVE NORMAL.

EXPECT THE LOW CLOUDS TO ONLY SLOWLY LIFT AND/OR SCATTER OUT FRIDAY
GIVEN THE CONTINUED E TO SE LOW LEVEL FLOW. THE ISOLATED SHRA AND
PATCHY DRIZZLE SHUD END BE MID MORNING...BEFORE PRECIP CHC INCREASES
FOR THE AFTERNOON. THERE WILL BE QUITE A BIT OF ELEVATED INSTABILITY
AS MID LEVELS COOL WITH THE DEVELOPING TROF OVER THE SE. HOWEVER...
ANY FORCING WILL BE WEAKER AS WILL THE INSTABILITY. THEREFORE...
EXPECT PRECIP COVERAGE TO BE ISOLATED OUTSIDE OF THE MTNS AND SCT
OVER THE MTNS WHERE DIFFERENTIAL HEATING AND SE FLOW WILL BE
STRONGER. HIGHS WILL BE A FEW DEGREES BELOW NORMAL...UNLESS CLOUDS
SCATTER OUT SOONER...WHICH WILL MAKE HIGHS CLOSER TO NORMAL.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
AS OF 230 PM EDT THURSDAY...THE SHORT TERM FORECAST PERIOD
INITIALIZES FRIDAY EVENING WITH THE MEAN UPPER PATTERN FEATURING A
TROF EJECTING OUT TO SEA OVER NOVA SCOTIA WHILE NEARLY ZONAL FLOW
PREVAILS WESTWARD INTO THE GREAT LAKES REGION.  A SECOND UPPER TROF
WILL BE AMPLIFYING AS IT EJECTS OUT OF SOUTH CENTRAL CANADA WITH A
COLD FRONT EXTENDING SOUTHWARD INTO THE NORTHERN PLAINS STATES.
CLOSER TO HOME...SURFACE RIDGING CENTERED OVER NEW ENGLAND WILL HAVE
WEDGED SOUTHWARD INTO NORTHEAST GA AND THE WESTERN CAROLINAS IN AN
EARLY FALL CAD REGIME.  EASTERLY UPSLOPE FLOW ALONG THE BLUE RIDGE
COMBINED WITH RATHER UNIMPRESSIVE ISENTROPIC UPGLIDE WILL WARRANT
MENTIONABLE POPS AT FORECAST INITIALIZATION.  THUS FOR FRIDAY
EVENING THE FORECAST FEATURES CHANCE LEVEL POPS ACROSS THE BLUE
RIDGE WITH ONLY SLIGHT CHANCE LEVELS RESIDING JUST EAST OF THE
FOOTHILLS.

POPS TAPER THROUGH THE OVERNIGHT LEADING TO A MOSTLY DRY FORECAST
FOR SATURDAY AS ABOVE MENTIONED CAD WEDGE BEGINS TO RETREAT YIELDING
ONLY SLIGHT CHANCE POPS ACROSS THE SOUTHERN TIER OF THE FORECAST
AREA WHERE BEST MOISTURE WILL RESIDE.  EXPECTING FORECAST TO REMAIN
DRY THROUGH THE OVERNIGHT INTO SUNDAY BEFORE POPS RAMP UP AHEAD OF
APPROACHING ABOVE MENTIONED UPPER TROF AND ASSOCIATED COLD FRONT.
SOUTHERLY MOISTURE ADVECTION WILL GRADUALLY RESUME ON SUNDAY HOWEVER
SHOULD NOT BE SUFFICIENT ENOUGH TO WARRANT EVEN ISOLATED/SCATTERED
PREFRONTAL CONVECTION.  THERE REMAINS SOME MODEL DISCONTINUITY
REGARDING THE TIMING OF THE INITIAL FRONTAL INTRUSION ON SUNDAY
EVENING WITH THE SLOWER NAM BEING THE OUTLIER.  THE GLOBAL GFS/ECMWF
ARE APPROX 6 HOURS FASTER WITH THE FRONTAL CONVECTION SLIDING INTO
THE NC MOUNTAINS BY THE END OF THE FORECAST CYCLE.  THEREFORE CHANCE
LEVEL POPS ARE FEATURED ALONG THE TN LINE WITH ONLY SLIGHT CHANCE
POPS RESIDING ACROSS THE REMAINDER OF THE WESTERN NC MOUNTAINS.  AS
FOR THE PIEDMONT REGIONS OF NC/SC...EXPECTING A DRY AND FAIRLY NICE
SUNDAY.  TEMPERATURES THROUGH THE SHORT TERM PERIOD WILL GRADUALLY
MODERATE TO AT OR JUST ABOVE NORMAL LEVELS AS THE LOW LEVEL FLOW
VEERS SOUTHERLY BY SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 1240 PM THU...LESS WARM AIR WILL ADVECT INTO THE REGION ON
MONDAY COINCIDENT WITH THE PASSAGE OF A MOISTURE LACKING COLD FRONT.
THERE REMAINS THE POSSIBILITY OF A ROUND OF MAINLY NC MTN SHOWERS
SUNDAY NIGHT AND MAYBE A FEW SHOWERS EAST OF THE BLUE SOMETIME ON
MONDAY. THE INFLUX OF POST FRONTAL DRIER AIR AND ENCROACHING SFC
RIDGE WILL RESULT IN DRY AND COOLER WX MONDAY NIGHT AND TUE AM MINS
ARE PROGGED TO BE ABT 5 DEG F BELOW CLIMO.

THE CWFA LOOKS TO BE WITHIN THE COOL CYCLONIC FLOW CLOSE TO THE
PERIPHERY OF THE EASTERN CONUS L/WV TROUGH ON TUESDAY WITH MODERATELY
STRONG SFC RIDGING BUILDING DOWN THE EASTERN SLOPES WEDNESDAY INTO
THURSDAY. WITHIN THIS DRY AND COOL PATTERN...TEMPERATURES SHOULD
AVERAGE 5 TO 8 DEG F BELOW CLIMO EACH DAY.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
AT KCLT...A PATCH OF MID/HIGH CLOUDS STREAMING OVERHEAD HAS PUT A
DAMPER ON MUCH OF THE CONVECTION ACROSS THE PIEDMONT...ALTHO AN
ISOLATED SHOWER IS STILL POSSIBLE. THIS WILL BE LEFT OUT OF THE TAF.
INSTEAD...EXPECT A SIMILAR PROGRESSION AS IN LAST NIGHT...WITH A LOW
CLOUD CEILING REDEVELOPING WITH THE LIGHT EASTERLY FLOW AT LOW
LEVELS. THE TAF HAS THIS HAPPENING PERHAPS A BIT TOO EARLY AT
02Z...BUT CONFIDENCE ONLY GOES UP FROM THERE. THINK THAT BY 05Z AN
MVFR CEILING IS LIKELY...AND THAT SHOULD EVENTUALLY DROP TO IFR
AROUND 10Z. KEPT THE VISIBILITY IN THE MVFR RANGE SIMILAR TO LAST
NIGHT...AND ANYTHING LOWER THAN THAT APPEARS UNLIKELY AS HIGH CLOUDS
WILL LIMIT FOG POTENTIAL. THE LOW CLOUD CEILING WILL BE SLOW TO LIFT
ONCE AGAIN FRIDAY MORNING AND IS NOT EXPECTED TO IMPROVE TO VFR
UNITL PERHAPS 18Z. WILL KEEP THE WIND NE THROUGH MOST OF THE DAY.

ELSEWHERE...SIMILAR CONDITIONS AS KCLT...ESPECIALLY KHKY. KAVL STILL
HAS THE BEST CHC OF SEEING LIFR OR VLIFR TOWARD MORNING...BUT TAF
WILL BE LIMITED MERELY TO IFR. ANOTHER MORNING WITH A SLOW RISE TO
LOW VFR THRU CIG RESTRICTIONS. STRONGER NELY WINDS DEVELOP OVERNIGHT
AND CONTINUE THRU FRI MORN. KAVL WILL SEE LIGHT SLY WIND DEVELOP
FRI. THERE IS A SLIGHTLY BETTER CHC FOR A SHOWER AT KAVL ON FRIDAY
AFTERNOON...SO A PROB30 WAS INCLUDED.

OUTLOOK...THE POTENTIAL FOR LATE NIGHT/MORNING FOG/STRATUS WILL
PERSIST INTO THE EARLY PART OF THE WEEKEND...ESPECIALLY IN THE MTN
VALLEYS. CONDITIONS MAY FINALLY DRY OUT FOR THE LATTER PART OF THE
WEEKEND. A COLD FRONT MAY BRING INCREASING CHANCES FOR SHOWERS/TSTMS
EARLY NEXT WEEK.

CONFIDENCE TABLE...

            01-07Z        07-13Z        13-19Z        19-01Z
KCLT       MED   63%     MED   64%     MED   74%     HIGH 100%
KGSP       HIGH  84%     MED   71%     MED   71%     HIGH  88%
KAVL       HIGH  93%     HIGH  81%     MED   77%     MED   69%
KHKY       MED   75%     MED   63%     HIGH  81%     HIGH  86%
KGMU       HIGH  87%     MED   67%     MED   67%     HIGH  86%
KAND       HIGH 100%     MED   75%     MED   73%     HIGH  92%

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...CSH
NEAR TERM...PM/RWH
SHORT TERM...CDG
LONG TERM...CSH
AVIATION...PM





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