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Local forecast by
"City, St"
  
000
FXUS62 KGSP 301803
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
203 PM EDT SAT AUG 30 2014

.SYNOPSIS...
A BERMUDA HIGH WILL DEVELOP AND LINGER INTO EARLY NEXT WEEK... 
RESULTING IN TYPICAL SUMMERTIME HEAT AND SCATTERED AFTERNOON 
THUNDERSTORMS EACH DAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1215 PM...LATEST CAM'S AND 12Z GFS/GEM CONTINUE WITH THE IDEA 
OF SCT CONVECTION DEVELOPING OVER NE GA AND THE SW MOUNTAINS BY MID 
AFTERNOON...WITH COVERAGE THEN SPREADING NE INTO THE CENTRAL 
MOUNTAINS AND PERHAPS THE NORTHERN MOUNTAINS DURING THE EVENING 
HOURS AS A WEAK SHORT WAVE MOVES THROUGH TN. THE 12Z NAM IS ALL 
ALONE IN DEVELOPING DEEP CONVECTION AND RESULTING HEAVY QPF OVER THE 
NC FOOTHILLS/PIEMDMONT LATE TONIGHT. THIS WILL BE REGARDED AS 
SPURIOUS AND NOT INCORPORATED INTO THE FORECAST. HAVE UPDATED MOST 
FIELDS FOR THIS AFTERNOON BY BLENDING IN LATEST CONSSHORT. THIS 
RESULTED IN ONLY MINOR CHANGES.   

AS OF 930 AM...SOME PATCHY DENSE FOG STILL HANGING IN THERE OVER 
PORTIONS OF THE UPPER FRENCH BROAD VALLEY...FOOTHILLS AND EVEN THE 
PIEDMONT. EXPECT THE FOG TO DISSIPATE BY ABOUT 1030 AM ALL AREAS. 
OTHERWISE...THE FORECAST IS IN GOOD SHAPE. LATEST CAMPOP STILL 
INDICATES THAT AT LEAST SCT CONVECTION SHOULD DEVELOP OVER WESTERN 
AREAS DURING THE MID TO LATE AFTERNOON HOURS. I BLENDED IN THE 
CAMPOP TO THE OFFICIAL FORECAST WHICH GENERALLY DELAYED THE ONSET OF 
CONVECTION SOMEWHAT AND RAISED THE POPS FOR THIS EVENING OVER THE SW 
MOUNTAINS AND NE GA. MADE ONLY MINOR ADJUSTMENTS TO OTHER FIELDS.

AS OF 630 AM EDT SATURDAY...EARLIER 2KFT STRATUS CLOUD DECK OVER 
WESTERN NC HAS RECEDED TO THE NORTH ALLOWING FOR JUST ENOUGH COOLING 
TO YIELD PATCHY FOG DEVELOPMENT/EXPANSION.  LATEST OBSERVATIONS 
ALONG WITH SATELLITE IMAGERY INDICATE LIGHT PATCHY FOG ACROSS 
PORTIONS OF THE NC PIEDMONT WHILE PATCHY DENSE FOG HAS DEVELOPED IN 
THE MOUNTAIN VALLEYS AS EXPECTED.  CONDITIONS WILL IMPROVE ACROSS 
THE PIEDMONT SHORTLY AFTER SUNRISE WITH THE MOUNTAIN VALLEY FOG 
PERSISTING FOR AN HOUR OR SO.  OTHERWISE....TWEAKED TEMPERATURES AND 
DEWPOINTS TO REFLECT LATEST OBSERVATIONS AND LEFT THE REMAINDER OF 
THE FORECAST AS IT WAS.  

PREVIOUS DISCUSSION...

AS OF 300 AM EDT SATURDAY...RATHER NICE DAY IN STORE ACROSS 
NORTHEAST GA AND THE WESTERN CAROLINAS AS DEEP LAYER RIDGING 
PREVAILS.  MEANWHILE...UPPER SHORT WAVE ENERGY TO THE WEST CONTINUES 
TO PROGRESS EAST ALONG THE MEAN FLOW PROMOTING DEVELOPMENT OF 
SURFACE TROF BENEATH AND SUSTAINED SOUTHERLY MOISTURE ADVECTION 
REGIME.  CLOSER TO HOME...REMNANT LOW LEVEL MOISTURE AXIS FROM OLD 
STATIONARY BOUNDARY CONTINUES TO PROVIDE A FOCUS FOR EXPANDING 
STRATUS CLOUD DECK.  LATEST MOS GUIDANCE CONTINUES TO SUPPORT PATCHY 
FOG DEVELOPMENT THIS MORNING ACROSS THE NC PIEDMONT WITH SOME AREAS 
OF DENSE FOG POSSIBLE IN AND AROUND THE MOUNTAIN VALLEYS.  THAT 
SAID...ABOVE MENTIONED STRATUS DECK WILL INHIBIT COOLING SOMEWHAT 
THEREBY DELAYING/PREVENTING FOG DEVELOPMENT FOR AREAS OF THE NC 
PIEDMONT.  

CONDITIONS WILL IMPROVE BEYOND DAYBREAK AS HEATING WORKS TO ERODE 
LOW STRATUS/FOG PRESENT ACROSS THE REGION.  LIGHT/CALM SURFACE FLOW 
WILL GRADUALLY INCREASE OUT OF THE SOUTHEAST TO AROUND 5-10MPH BY 
MID/LATE AFTERNOON.  SOUNDINGS CONTINUE TO INDICATE JUST ENOUGH LOW 
LEVEL MOISTURE TO SUPPORT MINIMAL COVERAGE OF FAIR WX CU AS LAPSE 
RATES STEEPEN WITH HEATING THIS AFTERNOON.  CONVECTION TO THE WEST 
ASSOCIATED WITH WAA CONVEYOR BELT AND SURFACE TROFFING WILL ALSO 
LIKELY PROMOTE SOME MID/HIGH LEVEL CIRRUS STREAMING ALOFT.  SPEAKING 
OF MOISTURE ADVECTION PATTERN...POPS WILL REMAIN NON MENTIONABLE 
THROUGH MUCH OF THE MORNING BEFORE GRADUALLY INCREASING TO NEAR 
LIKELY LEVELS ACROSS THE WESTERN MOST ZONES...TAPERING TO SLIGHT 
CHANCE LEVELS FOR PORTIONS OF THE WESTERN UPSTATE AND NC FOOTHILLS 
BY LATE EVENING.  THIS IS IN RESPONSE TO BOTH THE MOISTURE AXIS 
APPROACHING AND ALSO PROXIMITY OF SOUTHEAST RIDGE LEADING TO WEAKER 
INHIBITION FURTHER WEST.  THAT SAID...PROFILES SUPPORT ONLY MINIMAL 
CAPE AND WOULD LIKELY NOT YIELD ROBUST UPDRAFTS LEADING TO SUSTAINED 
CONVECTION.  THUS...ONLY EXPECTING GENERAL THUNDERSTORMS AT BEST 
WITH CLOUD TO GROUND LIGHTNING BEING A PRIMARY THREAT WHICH WILL BE 
MENTIONED IN THE HWO.  POPS WILL REMAIN AT SOLID CHANCE LEVELS 
ACROSS THE HIGH TERRAIN THROUGH THE OVERNIGHT HOURS TO ACCOUNT FOR 
CONTINUED SOUTHERLY UPSLOPE ENHANCED SHOWERS.  TEMPERATURES ON 
SATURDAY WILL WARM TO ABOVE NORMAL LEVELS ACROSS THE MAJORITY OF THE 
FORECAST AREA AS STRONG UPPER RIDGE PREVAILS.  ALTHOUGH STILL ABOVE 
NORMAL...TEMPERATURES COULD BE SLIGHTLY COOLER ACROSS THE MOUNTAINS 
AS BETTER SKY COVER LIMITS HEATING.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
AS OF 215 AM SATURDAY...A WEAKENING SHORT WAVE TROUGH EJECTING FROM 
THE GREAT PLAINS WILL PHASE WITH A SHORT WAVE CROSSING THE GREAT 
LAKES AND NUDGE THE SERN CONUS ANTICYCLONE OFF THE SE COAST EARLY IN 
THE SHORT TERM. A SECONDARY WEAK WAVE MOVES ACROSS THE AREA MONDAY 
AS THE ANTICYCLONE DROPS TO THE GA COAST AND RETROGRADES INTO GA MON 
NITE. AT THE SFC...A WEAKENING FRONTAL ZONE MOVES ACROSS THE AREA 
SUNDAY IN ASSOCIATION WITH THE SHORT WAVE. THERE WILL ALSO BE SOME 
UPPER DIVERGENCE AS THE RIGHT ENTRANCE REGION OF A JET STREAK MOVES 
THRU. HOWEVER...ALL GUIDANCE HAS BACKED OFF ON THE AMOUNT OF 
INSTABILITY DEVELOPING SUNDAY...AT LEAST OUTSIDE OF THE MTNS. CAP 
DOES ERODE DURING THE DAY...SO EXPECT CONVECTION TO DEVELOP. 
HOWEVER...POP HAS BEEN LOWERED OUTSIDE OF THE MTNS IN LINE WITH 
GUIDANCE CONSENSUS...BUT KEPT IN THE SCT RANGE AS THERE WILL BE SOME 
FORCING ALONG WITH WEAK INSTABILITY. WITH THE CONTINUED MODERATE 
INSTABILITY EXPECTED OVER THE MTNS...LIKELY POP IS RETAINED THERE. 
GUIDANCE ALSO IN AGREEMENT SHOWING LOWER PW VALUES THAN PREVIOUSLY 
FCST...LEADING TO ONLY ISOLATED POTENTIAL FOR HEAVY RAINFALL. ANY 
SVR STORMS SHUD BE ISOLATED AS WELL WITH WEAK SHEAR. TEMPS WILL BE 
NEAR TO SLIGHTLY ABOVE NORMAL.

ONLY WEAK INSTABILITY IS FORECAST ON MONDAY WITH LITTLE IN THE WAY 
OF FORCING. HAVE DROPPED POP ACROSS THE BOARD...BUT KEPT IN THE 
SCATTERED RANGE. STILL...THE BEST MOISTURE AND INSTABILITY WILL BE 
OVER THE MTNS...SO POP SLIGHTLY HIGHER THERE. TEMPS WILL WARM A FEW 
DEGREES MONDAY AND MONDAY NITE.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
AS OF 335 AM SATURDAY...A LOW AMPLITUDE TROF MOVES EAST ACROSS THE 
ERN CONUS TUE KEEPING THE UPPER ANTICYCLONE SUPPRESSED ACROSS THE 
GULF COAST STATES. AS THE TROF MOVES EAST OFF SHORE WED...RIDGING 
DEVELOPS OVER THE SERN CONUS. THIS RIDGING REMAINS IN PLACE THU AND 
FRI. AT THE SFC...A WEAK COLD FRONT DROPS SOUTH TOWARD THE AREA AS 
THE TROF MOVES EAST TUE. THE FRONT STALLS NORTH OF THE AREA WED... 
BUT A LEE TROF DEVELOPS OVER THE CWFA. THE FRONT DISSIPATES THU BUT 
LEAVES A WEAK CONVERGENCE ZONE WHICH MOVES IN ON THU AND REMAINS IN 
PLACE FRI. THIS PATTERN WILL KEEP LOW LEVEL MOISTURE AND INSTABILITY 
ACROSS THE AREA. EVEN WITH THE RIDGE IN PLACE...THE SFC BOUNDARY 
WILL HELP PROVIDE ENOUGH FORCING TO TAP THE ELEVATED INSTABILITY 
ACROSS THE AREA. THIS WILL LEAD TO GENERALLY SCT DIURNAL CONVECTION 
EACH DAY...WITH COVERAGE SLIGHTLY FAVORING THE MTNS THRU THE PERIOD. 
TEMPERATURES WILL REMAIN ABOVE NORMAL UNTIL FRI WHEN THEY DROP TO 
NEAR NORMAL.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
AT KCLT...GENERALLY VFR CONDITIONS WILL PREVAIL THROUGH THE PERIOD 
WITH SCT-BKN LOW VFR CLOUDS. LOOKS LIKE CONVECTION SHOULD REMAIN 
CAPPED DUE TO DEEP LAYER RIDGING OVER THE AREA. CONSIDERABLE 
BOUNDARY LAYER MOISTURE MAY ALLOW FOR SOME MVFR FOG RESTRICTIONS 
CIRCA 12Z.

ELSEWHERE...GENERALLY VFR CONDITIONS WILL PREVAIL THROUGH THE  
FORECAST PERIOD. SIGNIFICANT RESTRICTIONS DUE TO FOG APPEAR LESS 
LIKELY EARLY SUNDAY DUE TO INCREASED CLOUD COVER. HOWEVER WITH 
CONSIDERABLE BOUNDARY LAYER MOISTURE IN PLACE...MVFR RESTRICTIONS 
ARE POSSIBLE. THE BEST CHANCE FOR THUNDERSTORMS WILL BE OVER THE 
MOUNTAINS THIS AFTERNOON AND EVENING...SO HAVE CARRIED A VCTS AT 
KAVL.

OUTLOOK...GENERALLY VFR CONDITIONS ARE EXPECTED THROUGH EARLY NEXT 
WEEK WITH THE EXCEPTION FOR RESTRICTIONS IN THE EARLY MORNING DUE TO 
LOW CLOUDS AND FOG...PRIMARILY IN THE MOUNTAIN VALLEYS. DIURNAL 
CONVECTION IS EXPECTED EACH AFTERNOON WITH THE MOST COVERAGE OVER 
THE MOUNTAINS.

CONFIDENCE TABLE...

            18-24Z        00-06Z        06-12Z        12-18Z 
KCLT       HIGH 100%     HIGH 100%     HIGH  93%     HIGH  89%     
KGSP       HIGH 100%     HIGH 100%     HIGH  87%     HIGH  89%     
KAVL       HIGH 100%     HIGH  97%     MED   64%     HIGH  80%     
KHKY       HIGH 100%     HIGH 100%     HIGH  88%     HIGH  92%     
KGMU       HIGH 100%     HIGH 100%     HIGH  98%     HIGH  98%     
KAND       HIGH 100%     HIGH 100%     HIGH 100%     HIGH  94%     

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...RWH
NEAR TERM...LG
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...LG





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Weather Forecast Office Greenville-Spartanburg
GSP International Airport
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Greer, SC 29651
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Page last modified: January 20, 2010

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