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Local forecast by
"City, St"
  
000
FXUS62 KGSP 180753
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
353 AM EDT WED MAR 18 2015

.SYNOPSIS...
COOL CANADIAN HIGH PRESSURE WILL SPREAD OVER THE AREA TODAY. DEEP 
LAYER MOISTURE ASSOCIATED WITH A WEAK SURFACE LOW WILL THEN 
OVERSPREAD THE AREA FROM THE WEST LATER TONIGHT AND THURSDAY AND 
LINGER THROUGH THE END OF THE WEEK. SOME TEMPORARY DRYING IS 
EXPECTED ON SATURDAY WITH PRECIPITATION CHANCES INCREASING AGAIN ON 
SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 320 AM EDT...CONDITIONS ARE MOSTLY QUIET ACROSS THE FCST AREA 
AS OF 7Z. WIND GUSTS HAVE PRETTY MUCH CEASED OVER ALL AREA EXCEPT 
FOR SOME SPORADIC GUSTS OVER THE NORTHERN AND CENTRAL NC MTS. THOSE 
SHOULD TAPER OFF OVER THE NEXT FEW HOURS. HIGH CLOUDS HAVE INCREASED 
IN COVERAGE SINCE THE LAST UPDATE A COUPLE HOURS AGO...YET THEY ARE 
ONLY SCT AT BEST FOR MOST SITES. TEMPS ARE ON TRACK TO BOTTOM OUT 
ABOUT 5 TO 10 DEGREES COOLER THAN YESTERDAY WITH SOME OF THE HIGHER 
TERRAIN DROPPING CLOSE TO FREEZING. WITH PREVAILING CAA AND 
DIMINISHING THICKNESSES TODAY...HIGHS WILL BE ROUGHLY 15 TO 20 
DEGREES COOLER TODAY COMPARED TO YESTERDAY. AS FOR THE BIG 
PICTURE...THE SFC HIGH WILL SLIDE FARTHER SE THRU THE DAY AS WINDS 
VEER AROUND TO NE AND THEN EVENTUALLY SE BY LATE TONIGHT. CLOUD 
COVER WILL STEADILY INCREASE THRU THE DAY FROM WEST TO EAST AS THE 
WEAK SFC LOW APPROACHES THE CAROLINAS AND THE DEEP MOISTURE PLUME 
MOVES INTO THE CWFA. THE LATEST MODEL GUIDANCE HAS BEEN SLOWING DOWN 
THE PROGRESSION OF THE LOW JUST A BIT AND THUS...I DONT THINK THE 
DEEPER MOISTURE WILL OVERSPREAD THE AREA AS SOON AS PREVIOUSLY 
THOUGHT...IE...ABOUT 4 TO 6 HRS SLOWER NOW. AT ANY RATE...BY THE END 
OF PERIOD AT 12Z THURS...DEEP LYR MOISTURE SHOULD BE OVER THE ENTIRE 
CWFA WITH BKN TO OVC CIGS PREVAILING. POPS WERE ALSO DIALED BACK A 
BIT WITH THE FIRST MENTION OF LIKELY NOT UNTIL ABOUT 6 OR 7Z THURS 
AND JUST OVER THE FAR SW ZONES. BY 12Z...I HAVE ALL ZONES AT 50% OR 
HIGHER WITH LIKELY TO CATEGORICAL OVER THE WESTERN 2/3 OF THE CWFA. 
QPF WILL BE MINIMAL BY THAT TIME WITH NO MORE THAN 0.1 TO 0.2 INCHES 
ANTICIPATED.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 225 AM WEDNESDAY...GUIDANCE IN PRETTY GOOD AGREEMENT ON A 
SHORT WAVE CROSSING THE AREA THURSDAY AND THE ASSOCIATED SFC LOW 
TRACKING ALONG THE GULF COAST...WHILE HIGH PRESSURE SETS UP IN A CAD 
CONFIGURATION. COPIOUS LOW LEVEL MOISTURE AND ISENTROPIC LIFT MOVE 
INTO THE AREA THU...BRINGING WIDESPREAD RAINFALL BY THE AFTERNOON. 
THE ISENTROPIC LIFT CONTINUES THRU THE EVENING KEEPING THE 
WIDESPREAD RAIN OVER THE AREA. THE LIFT BEGINS TO WEAKEN OVERNIGHT 
WITH DECREASING PRECIP CHC FROM SW TO NE ACROSS THE AREA. DESPITE 
THE WIDESPREAD RAINFALL...QPF AMOUNTS WILL BE RELATIVELY LIGHT 
AROUND HALF AN INCH. HIGHS WILL BE 15 TO 20 DEGREES BELOW NORMAL 
WITH THE RAIN AND DEVELOPING CAD...WHILE LOWS WILL BE UP TO 5 
DEGREES ABOVE NORMAL.

FRIDAY IS THE TRICKIER FCST AS THE GUIDANCE IS IN SOME DISAGREEMENT 
ON CAD EROSION AND THE PRECIP COVERAGE AS ANOTHER SHORT WAVE CROSSES 
THE AREA. THERE IS QUITE A BIT OF MOISTURE EARLY...WITH DRYING LATE. 
THERE IS LITTLE IN THE WAY OF ISENTROPIC LIFT...BUT A DECENT AMOUNT 
OF SYNOPTIC SCALE LIFT EARLY. THEREFORE...USED A GUIDANCE BLEND 
WHICH SUGGESTS LINGERING PRECIP FRI MORNING WITH DIMINISHING 
COVERAGE DURING THE AFTERNOON...AND PRECIP ENDING DURING THE 
EVENING. HIGHS SHUD WARM WITH CAD EROSION AND DIMINISHING PRECIP 
COVERAGE. HOWEVER...CLOUDY SKIES REMAIN KEEPING HIGHS FROM 5 TO 10 
DEGREES BELOW NORMAL...WITH LOWS 5 TO 10 DEGREES ABOVE NORMAL AS 
WELL.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 350 AM WEDNESDAY...GUIDANCE HAS COME INTO BETTER AGREEMENT ON 
THE OVERALL PATTERN THRU THE MEDIUM RANGE...BUT SOME DETAIL 
DIFFERENCES LINGER. A SRN STREAM SHORT WAVE CROSSES THE AREA MONDAY 
WHILE A NRN STREAM SHORT WAVE CROSSES THE AREA TUESDAY...FOLLOWED BY 
RIDGING FOR WED. AT THE SFC...DRY HIGH PRESSURE BRIEFLY BUILDS IN ON 
SATURDAY...WHILE A GULF LOW PRESSURE SYSTEM MOVES SOUTH OF THE AREA 
SUNDAY. LOW LEVEL MOISTURE AND ISENTROPIC LIFT RETURN WITH THIS 
SYSTEM...BUT THE BEST PRECIP CHANCES REMAIN ALONG AND SOUTH OF I-85. 
THE SFC LOW MOVES OFF SHORE ON MONDAY WITH HIGH PRESSURE REMAINING 
RIDGED INTO THE AREA. LOW LEVEL MOISTURE AND LIFT RETURN OVER THE 
SFC HIGH AND CONTINUES THRU TUE AS A SHORT WAVE TOPS THE RIDGE AND 
MOVES OVER THE AREA. AGAIN...HAVE GONE WITH A MDL BLEND FOR POP THRU 
THE PERIOD...WHICH KEEPS CHC POP LIMITED TO THE EXTREME SRN CWFA SAT 
NITE AND SUN...WITH SLIGHT CHC POP ELSEWHERE. POP IS NO HIGHER THAN 
SLIGHT CHC THRU THE REST OF THE PERIOD GIVEN THE UNCERTAINTY. 
ALTHOUGH TEMPS ARE COLD ENUF FOR SOME RAIN OR SNOW ACROSS THE NC 
MTNS AT TIMES...THIS REMAINS VERY UNCERTAIN. ABOVE NORMAL HIGHS SAT 
FALL TO NEAR NORMAL SUN...THEN BELOW NORMAL MON AND TUE. LOWS FOLLOW 
A SIMILAR TREND...BUT WARM BACK TOWARD NORMAL BY TUE NITE.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
KCLT AND ELSEWHERE...VFR CONDITIONS EXPECTED THRU TAF PERIOD. 
GUSTY NW WINDS HAVE BEEN DIMINISHING OVER THE PAST FEW HOURS WITH 
SOME SITES IN THE NC MTS AND NORTHERN FOOTHILLS STILL REPORTING 
SPORADIC GUSTS IN THE 15 TO 20KT RANGE. WINDS SHOULD WEAKEN OVER THE 
NEXT 6 HRS OR SO WITH MOUNTAIN SITES SEEING THE GREATEST DECLINE 
LATER IN THE MORNING. WINDS SHOULD ALSO GRADUALLY VEER TO MORE OF A 
NELY DIRECTION LATER IN THE MORNING AS HIGH PRESSURE BUILDS IN FROM 
THE NORTH. THE HIGH WILL SLIDE EAST BY MID AFTERNOON AND WINDS WILL 
CONTINUE TO VEER AROUND FROM SE TO SSE. HIGH CLOUDS WILL INCREASE 
FROM THE WEST DURING THE LATER PORTION OF THE PERIOD AS THE DEEPER 
MOISTURE APPROACHES THE REGION. OVERALL...THE LATEST GUIDANCE HAS 
BEEN SLOWING THE EASTWARD ADVANCEMENT OF THE MOISTURE PLUME AND ITS 
LOOKING LIKE CIGS WONT DROP BELOW 9000FT OVER MOST OF THE FCST AREA 
UNTIL JUST AFTER THE TAF PERIOD ENDS. REGARDLESS...KCLT SHOULD BE 
THE LAST TO DROP CIGS BELOW HIGH LEVELS AND THERE IS LITTLE CHANCE 
OF ANY MVFR VALUES BEFORE 6Z. ADDITIONALLY...I DONT EXPECT ANY SIG 
PRECIP UNTIL AFTER 10Z OR SO.    
 
OUTLOOK...A WEAK LOW PRESSURE SYSTEM WILL MOVE EASTWARD ALONG A 
STALLED FRONT SOUTH OF THE AREA...INCREASING MOISTURE AND PRECIP 
CHANCES ALONG WITH THE PROBABILITY OF RESTRICTIONS THURS MORNING.  
BRIEF DRYING IS EXPECTED FOR THE EARLY PART OF THE WEEKEND...YET 
UNSETTLED CONDITIONS RETURN LATE IN THE WEEKEND.

CONFIDENCE TABLE...

            08-14Z        14-20Z        20-02Z        02-06Z 
KCLT       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAVL       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KHKY       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KGMU       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAND       HIGH 100%     HIGH 100%     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...JPT
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...JPT


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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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