Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 112129
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
529 PM EDT FRI JUL 11 2014

.SYNOPSIS...
A WEAK FRONTAL BOUNDARY WILL GRADUALLY WEAKEN AND DISSIPATE
OVERNIGHT WITH WEAK HIGH PRESSURE RETURNING FOR THE WEEKEND. AN
UNSEASONABLY STRONG COLD FRONT IS THEN EXPECTED TO REACH THE WESTERN
CAROLINAS BY TUESDAY INCREASING THE POSSIBILITY OF WIDESPREAD
THUNDERSTORMS.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 525 PM...LATEST SATELLITE IMAGES CONTINUE TO INDICATE
ENHANCED CU ACROSS THE MTNS AND ADJACENT FOOTHILLS. THE CU ALONG AND
EAST OF I-85 AND I-77 APPEARED TO BE SMALL CELLS WITH SHALLOW
VERTICAL DEVELOPMENT. KGSP RADAR INDICATED A FEW SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS THE EAST FACING SLOPES...THE GREATEST
COVERAGE WAS NEAR THE NC/GA/SC STATE LINE INTERSECTION. I WILL
UPDATE THE FORECAST TO ADJUST POPS AND ALIGN TEMPERATURES TO
OBSERVATIONS.

AS OF 230 PM EDT FRIDAY...QUASI STATIONARY SURFACE FRONTAL BOUNDARY
REMAINS IN PLACE ACROSS THE MIDLANDS OF SC..EASTWARD INTO THE
SANDHILLS AND COASTAL PLAINS OF NC.  DESPITE THE WEAK FROPA...NOT
MUCH HAS CHANGED THERMODYNAMICALLY ACROSS THE CWFA TODAY.  DEWPOINTS
REMAIN IN THE UPPER 60S TO LOWER 70S WITH MODEST HEATING ALLOWING
FOR CONDITIONAL DESTABILIZATION.  UPPER RIDGE BUILDING IN OVER THE
SOUTHERN PLAINS CONTINUES TO STRETCH EASTWARD ALLOWING FOR HEIGHTS
TO RISE OVER THE SOUTHEAST.  THUS...FORECAST SOUNDINGS INDICATE
IMPROVING MID LEVEL SUBSIDENCE LEADING TO A PARTIALLY CAPPED
ENVIRONMENT.  KEPT POPS AT SOLID CHANCE LEVELS ACROSS THE BLUE RIDGE
THIS AFTERNOON TAPERING TO NO MENTIONABLE POPS EASTWARD INTO THE
NC/SC PIEDMONT REGIONS WHERE CAPPING SHOULD HOLD.  NOT EXPECTING ANY
OF THE MTN SHOWERS/THUNDERSTORMS TO DEVELOP ANY DEEP UPDRAFTS WHICH
WILL LIMIT LONGEVITY AND INTENSITY.  THAT SAID...ABUNDANT DCAPE IN
THE REGION COULD YIELD A MODEST MICROBURST THREAT ALONG WITH
FREQUENT CLOUD TO GROUND LIGHTNING WITH THE STRONGER CELLS.

THINGS WILL QUIET DOWN OVERNIGHT AS HEATING IS LOST AND WEAK UPSLOPE
FLOW SUBSIDES.  GUIDANCE INDICATES THE MOIST BOUNDARY LAYER WILL
DECOUPLE ALLOWING FOR LOW STRATUS AND/OR FOG TO DEVELOP IN AND
AROUND THE MOUNTAIN VALLEYS...AND POTENTIALLY TO A LESSER DEGREE
ACROSS THE NC PIEDMONT.  TYPICAL SUMMERTIME PATTERN RETURNS ON
SATURDAY AS HIGH PRESSURE ACROSS THE NORTHEAST GIVES WAY TO THE
BERMUDA HIGH.  IN RESPONSE...STRONG SOUTHEASTERLY FLOW WILL RETURN
LEADING TO A DIURNAL POP/TEMPERATURE TREND.  FORECAST WILL FEATURE
CHANCES POPS IN THE CLIMO FAVORED REGIONS OF THE HIGH TERRAIN WHERE
UPSLOPE ENHANCEMENT OCCURS...ALONG WITH SLIGHT CHANCE POPS ALONG THE
SOUTHERN TIER OF THE CWFA WHERE SURFACE CONVERGENCE ALONG OLD
STATIONARY FRONT COULD INITIATE SHOWERS/THUNDERSTORMS AS ABOVE
MENTIONED SOUTHEASTERLY FLOW MIGRATES THE FRONT NORTH.  TEMPERATURES
THROUGH THE PERIOD WILL REMAIN AT OR JUST ABOVE NORMAL LEVELS.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
AS OF 145 PM FRI...LATEST GUIDANCE STILL SUGGESTS THAT THE SHORT
TERM WILL FEATURE RATHER TYPICAL JULY WEATHER FOR THE WESTERN
CAROLINAS AND NE GA. HIGH PRESSURE WILL REMAIN RIDGED OVER THE AREA
SATURDAY THROUGH SUNDAY AS A WESTWARD EXTENSION OF THE BERMUDA HIGH.
THE HIGH WILL BEGIN TO BREAK DOWN OVER THE AREA ON MONDAY AS HEIGHTS
BEGIN TO FALL ACROSS THE EASTERN U.S. IN RESPONSE TO A STRONG UPPER
LOW DROPPING SOUTHEAST OUT OF CANADA TOWARD THE GREAT LAKES.
HENCE...A MORE PROMINENT LEE TROUGH IS SHOWING UP IN THE MODEL
GUIDANCE FOR MONDAY...WHICH SHOULD SERVE AS A TRIGGER FOR MORE
CONVECTION OVER THE PIEDMONT THAN ON PREVIOUS DAYS. TO
SUMMARIZE...ON SUNDAY AFTERNOON CONVECTION SHOULD BE MOSTLY CONFINED
TO THE UPSLOPE AREAS IN THE MOUNTAINS...WHILE ON MONDAY ALL AREAS
SHOULD SEE SCATTERED CONVECTION DURING THE AFTERNOON. MAX TEMPS
SUNDAY AND MONDAY WILL BE AT OR A DEGREE OR TWO ABOVE CLIMO NORMALS.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM FRI...ONE THING THAT THE MEDIUM RANGE GUIDANCE
CONTINUES TO AGREE UPON IS THE DISTINCT UPPER LEVEL PATTERN CHANGE
THAT IS FORECAST TO OCCUR IN THE EARLY TO MID WEEK PERIOD ACROSS THE
EASTERN PART OF THE NATION. A DEEP UPPER LOW IS STILL FORECAST TO
SWING SOUTH OUT OF NORTHERN CANADA AND ESTABLISH AN ANOMALOUS UPPER
TROUGH OVER THE EAST BY MIDWEEK. HOWEVER...THE DETAILS ARE BECOMING
A LITTLE MORE MURKY IN OUR REGION AS THE 12Z GFS HAS GONE OUT ON ITS
OWN IN REGARD TO FRONTAL TIMING, POSITION AND FRONTAL WAVE
DEVELOPMENT. THE 12Z GFS IS FASTER THAN ITS PREVIOUS RUNS AND WITH
THE CMC/ECF IN MOVING THE UPPER LOW INTO THE GREAT LAKES...AND IT
DOES NOT MOVE THE LOW AS FAR SOUTH. IN FACT...IT KEEPS THE UPPER LOW
CENTER ACROSS THE NORTHERN LAKES. THIS OF COURSE ULTIMATELY AFFECTS
HOW FAR SOUTH THE SURFACE COLD FRONT CAN BE DRIVEN. THE 12Z GFS
MOVES THE COLD FRONT INTO THE NC MOUNTAINS MONDAY NIGHT...THEN
STALLS THE BOUNDARY SOMEWHERE ACROSS THE PIEDMONT ON TUE. THEN IT
DEVELOPS A SERIES OF FRONTAL WAVES TUE-THU WITH WIDESPREAD PRECIP
EACH DAY. WPC ON THE OTHER HAND HAS GONE WITH A MORE EC/CMC SOLUTION
WHICH BRINGS THE FRONT INTO THE AREA ON TUE AND MOVES THE FRONT FAR
ENOUGH SOUTH OF THE AREA TO ALLOW DRIER AIR TO WORK INTO THE REGION
WED INTO THU. ALTHOUGH THE 00Z GFS ENSEMBLE IS ALSO FARTHER NORTH
WITH THE FRONTAL BOUNDARY...IT IS NOT AS FAR NORTH AS THE 12Z
OPERATIONAL POSTIION. AT THIS JUNCTURE...WE PREFER TO TREND
TOWARD THE WPC SOLUTION WHICH IS MORE CONSISTENT WITH PREVIOUS
FORECASTS. WE WILL LINGER SOME POPS OVER MOST OF THE AREA ON WED DUE
TO THE UNCERTAINTY INVOLVED...BUT WILL ALLOW FOR A DRY DAY ON THU.
WILL PROBALBY FEATURE CLIMO POPS ON FRI AS THE FRONT MAY BEGIN TO
RETURN NORTHWARD.

IN REGARD TO IMPACTS...THE FRONT WILL BE WELL FORCED FOR JULY AND
CAPES COULD POOL AHEAD OF THE FRONT TO PERHAPS 1500-2000J/KG
DEPENDING ON TIMING...SO THERE IS A POSSIBILITY FOR AN ORGANIZED
SEVERE STORM EVENT WITH THE FRONTAL PASSAGE. WIND SHEAR WILL BE
RATHER GOOD FOR JULY WITH FORECAST SOUNDINGS FEATURING UP TO 30-40KT
OF 0-6KM BULK SHEAR. ALSO...TEMPS ARE STILL EXPECTED TO BE AT LEAST 2
STANDARD DEVIATIONS BELOW AVERAGE WED AND THU. FOR INSTANCE...THE
12Z CONSRAW GUIDANCE FOR WED HAS MAX TEMPS CLOSE TO 10 DEGREES BELOW
CLIMO.

TO SUMMARIZE...A STRONG COLD FRONT IS FORECAST TO ARRIVE ON TUESDAY
BRINGING THE POTENTIAL FOR SEVERE THUNDERSTORMS. MUCH  COOLER WEATHER
IS EXPECTED WED AND THU WITH A LINGERING CHANCE FOR SHOWERS ON WED.
THU MAY BE A DRY DAY...THEN A CHANCE FOR SHOWERS/STORMS WILL RETURN
FOR FRIDAY.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
AT KCLT...VFR CONDITIONS WILL PREVAIL THROUGH THE MAJORITY OF THE
FORECAST CYCLE AS UPPER HEIGHTS RISE LEADING TO BUILDING
SUBSIDENCE.  THUS...NO WX IS FORECAST THROUGH THE PERIOD.  BKN LOW
LEVEL CU WILL PERSIST THROUGH THE AFTERNOON BEFORE SCT OUT AFTER
COOLING SUBSIDES.  GUIDANCE HINTS AT LOW STRATUS AND FOG DEVELOPMENT
OVER THE NC PIEDMONT BY MID MORNING AS THE MOIST BOUNDARY LAYER
DECOUPLES. THEREFORE INCLUDED FM GROUP FOR MVFR LEVEL FOG AND AN
MVFR LEVEL SCT CLOUD DECK.  BY MID/LATE MORNING RESTRICITIONS WILL
LIFT AND CONDITIONS WILL IMPROVE BACK TO VFR LEVELS THROUGH THE
PERIOD.  WINDS WILL REMAIN A LITTLE TRICKY IN THE NEAR TERM HOWEVER
SHOULD BE PREDOMINATELY NE BEFORE QUICKLY VEERING SOUTHERLY THROUGH
THE TAF CYCLE.

ELSEWHERE...MUCH THE SAME AS KCLT ABOVE AS VFR CONDITIONS PREVAIL
OUTSIDE OF MVFR/IFR/LIFR FOG RESTRICITONS ON SATURDAY MORNING AT ALL
SITES...AND POTENTIAL RESTRICTIONS TO DUE CONVECTION AT KAVL THIS
AFTERNOON.  PREVAILED ALL SITES WITH NO WX THIS AFTERNOON ASIDE FOR
VCTS MENTION AT KAVL DUE TO MOUNTAIN UPSLOPE INDUCED CONVECTION.
ADDED MVFR/IFR LEVEL VSBY RESTRICITONS DUE TO FOG AT ALL SC
SITES...ALONG WITH IFR/LIFR CONDITIONS AT KHKY AND KAVL BY EARLY/MID
MORNING.  OTHERWISE...WINDS WILL VEER FROM THE NE TO MORE OF A
SOUTHERLY COMPONENT THROUGH THE PERIOD.

OUTLOOK...HIGH PRESSURE WILL SLOWLY SETTLE OVER THE AREA THIS
WEEKEND. ANY RESTRICTIONS SHOULD MAINLY BE CONFINED TO DIURNAL TSTMS
AND MORNING VALLEY FOG EACH DAY.

CONFIDENCE TABLE...

            21-03Z        03-09Z        09-15Z        15-21Z
KCLT       HIGH 100%     HIGH  84%     LOW   46%     HIGH 100%
KGSP       HIGH 100%     HIGH  84%     LOW   51%     HIGH 100%
KAVL       HIGH 100%     MED   75%     MED   62%     HIGH 100%
KHKY       HIGH 100%     HIGH  88%     MED   62%     HIGH 100%
KGMU       HIGH 100%     HIGH  84%     LOW   59%     HIGH 100%
KAND       HIGH 100%     HIGH  84%     LOW   58%     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...DEO
NEAR TERM...CDG/NED
SHORT TERM...LG
LONG TERM...LG
AVIATION...CDG






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