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Local forecast by
"City, St"
  
000
FXUS62 KGSP 022150
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
450 PM EST MON MAR 2 2015

.SYNOPSIS...
COOL CANADIAN HIGH PRESSURE WILL BUILD INTO THE REGION THROUGH 
TUESDAY...BUT MOIST AND MILDER AIR SHOULD BE BACK ON WEDNESDAY OUT
AHEAD AN APPROACHING COLD FRONT. THIS FRONT IS FORECAST TO PASS 
THROUGH THE AREA ON THURSDAY...DRYING US OUT BY THURSDAY NIGHT.

&&

.NEAR TERM /THROUGH TUESDAY/...
AS OF 430 PM...UPDATED THE GRIDS TO ACCOUNT FOR PEAK TEMPS ACROSS
THE AREA RUNNING WARMER THAN THE FCST GRIDS. OBSERVED WINDS ARE A
CAT OR SO STRONGER ACROSS THE NC PIEDMONT ASSOCIATED WITH THE
BACKDOOR FRONT AND HAVE BEEN UPDATED. STILL EXPECT ISOL/SCT -RA TO
REACH THE SW/RN ZONES BY 00Z.

AS OF 230 PM...THE TARDY BACK DOOR COLD FRONT CONTINUES TO WREAK 
HAVOC UPON THE TEMPERATURE FORECAST THIS AFTERNOON...WITH TEMPS ONCE 
AGAIN RUNNING ABOUT TWO CATEGORIES WARMER THAN FCST AS OF 19Z. WILL 
SIGNIFICANTLY BUMP TEMPS UP ONCE MORE...AND ADJUST TO THE TREND THAT 
WAS TAKEN FROM A SUPER-BLEND OF GUIDANCE STARTING EARLY THIS 
EVENING. NOT SEEING MUCH IN THE WAY OF PRECIP DEVELOPMENT YET...SO 
POP TREND WAS ALSO KNOCKED DOWN.

WHAT WE HAVE OVER THE NEXT 24 HOURS IS ANOTHER NUISANCE-TYPE 
SITUATION DEVELOPING EARLY TUESDAY MORNING...MAINLY OVER THE NRN 
FOOTHILLS AND NRN MTNS OF NC. IN THE BIGGER PICTURE...A BROAD UPPER 
RIDGE WILL BUILD IN FROM THE WEST TONIGHT...WITH THE UPPER RIDGE 
AXIS MOVING OVERHEAD MIDDAY ON TUESDAY. A WEAK UPPER WAVE WILL TOP 
THE RIDGE AND MOVE THROUGH ON TUESDAY MORNING. THE MAIN PROBLEM 
ARISES WHEN THE UPPER RIDGE CARRIES A COLD DRY SURFACE HIGH PAST TO 
THE N THIS EVENING AND THEN INTO A POSITION OVER THE MID ATLANTIC ON 
TUESDAY MORNING TO SUPPORT A HYBRID COLD AIR DAMMING EVENT. LOW 
LEVEL MOISTURE RETURN AND ISENTROPIC UPGLIDE COMMENCE ON THE BACK 
SIDE OF THE HIGH AND OVER THE TOP OF THE OLD BACK DOOR COLD FRONT 
LATE TONIGHT. PRECIP MAY DEVELOP AS EARLY AS THIS EVENING ACROSS THE 
SAVANNAH RIVER BASIN/UPSTATE/SRN NC MTNS AS THE UPGLIDE BEGINS. WILL 
START WITH A CHANCE POP THERE AND GRADUALLY EXPAND/INCREASE THE 
POP...FAVORING THE BLUE RIDGE. AS IN THE PREVIOUS FCST...THERE WILL 
BE A SLIVER OR AREA OF TEMPS THAT DROP DOWN TO SOMETHING SUB-
FREEZING MAINLY NEAR THE BLUE RIDGE N OF I-40 AFTER MIDNIGHT. PRECIP 
AMTS WILL BE LESS THAN ONE TENTH OF AN INCH AND PROBABILITY IS 
LIKELY AT BEST...BUT THE PRECIP TYPE WOULD BE FREEZING RAIN/DRIZZLE. 
THINK IT BEST TO RAISE A FREEZING RAIN ADVISORY FOR THAT REGION FOR 
LATE TONIGHT/TUESDAY MORNING. TEMPS WILL RISE ABOVE FREEZING BY LATE 
MORNING. THE REST OF AREA SHOULD REMAIN ABOVE FREEZING. WILL HOLD 
ONTO A LIKELY POP FOR THE BALANCE OF TUESDAY MAINLY OVER THE WEST... 
WITH A CHC OVER THE EASTERN FRINGE. TEMPS ON TUESDAY WILL SEEM LIKE 
A CRUEL JOKE...NEARLY 20 DEGREES COLDER THAN TODAY...WITH A NE WIND.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AT 300 PM EST MONDAY...THE SHORT TERM FCST PERIOD INITIALIZES 
TUESDAY EVENING AMONGST WEAK UPPER RIDGING ALOFT OVER THE 
EAST...WHILE A TROF SLIDES THROUGH THE NORTHERN PLAINS.  AT THE 
SURFACE...A POTENT COLD FRONT WILL BE SLIDING THROUGH THE OHIO 
VALLEY WHILE A MODEST WARM SECTOR ESTABLISHES ITSELF OVER THE 
SOUTHEAST AIDED BY SOUTHERLY FLOW AROUND WESTERN ATLANTIC SURFACE 
RIDGE.  THE FCST INITIALIZES WITH LIKELY POPS ACROSS THE MTNS DUE TO 
SOUTHERLY UPSLOPING WHILE LOWER MID RANGE CHANCE POPS ARE FEATURED 
FURTHER EAST.  POPS WILL DECREASE THROUGH THE OVERNIGHT ACROSS THE 
EASTERN TIER OF THE FCST AREA WHILE SOLID LIKELY POPS REMAIN OVER 
THE HIGH TERRAIN INTO WEDNESDAY.

MODELS CONTINUE TO INDICATE SOME DESTABILIZATION IN THE WARM SECTOR 
ACROSS THE MTNS ON WEDNESDAY AHEAD OF THE FRONT...THUS ADDED MENTION 
OF THUNDER WHERE NEEDED ALTHOUGH NO DEEP ORGANIZED CONVECTION IS 
FCST.  OUTSIDE OF THE MTNS ONLY SHOWERS WERE MENTIONED. POPS WILL 
GRADUALLY INCREASE ACROSS THE ENTIRE REGION WEDNESDAY NIGHT INTO 
THURSDAY AS THE FROPA OCCURS LEADING TO SOLID LIKELY POPS BY EARLY 
MORNING THURSDAY.  AT THAT POINT...THE PRIMARY FOCUS OF THE PERIOD 
BECOMES WINTRY WEATHER CONCERNS ALONG THE NC MTN ZONES NEAR THE TN 
LINE.   MODELS INDICATE A PERIOD WHEN THERMAL PROFILES YIELD A 
SUBFREEZING LAYER NEAR THE SURFACE...AHEAD OF THE DEEPER COLD 
ADVECTION ALOFT.  THE NAM BEING THE MOST AGGRESSIVE WITH SUCH WOULD 
YIELD A PROLONGED PERIOD OF FZRA ACROSS THE SPINE OF THE 
APPS...BEFORE A CHANGE OVER TO ALL SNOW.  THE GFS LEANED TOWARDS A 
FASTER COLD ADVECTION PATTERN...THUS A SHORTER PERIOD OF FZRA.  
OPTED FOR THE GFS SOLUTION...WHICH HAPPENED TO BE MUCH ALIGNED WITH 
THE NEW ECMWF.  THEREFORE...FCST FEATURES A PERIOD OF FZRA ALONG THE 
TN LINE ON THURSDAY MORNING...BEFORE A PHASE CHANGE OCCURS TO 
SLEET...THEN ALL SNOW.  TOTAL SNOW AND ICE ACCUMULATIONS REMAIN 
BELOW ADVISORY CRITERIA AT THIS POINT THEREFORE WILL NOT MENTION IN 
HWO. FURTHER EAST ALONG THE FRONT...PROFILES WILL REMAIN SUPPORTIVE 
OF ALL RAIN PROCESSES WITH POPS DECREASING INTO THE LATE AFTERNOON 
HOURS.  TEMPERATURES ON WEDNESDAY WILL BE ABOVE NORMAL AMONGST WAA 
REGIME...WHILE BELOW NORMAL TEMPERATURES RETURN POST FROPA ON 
THURSDAY.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 200 PM MON...SFC FRONT WILL DEPART THE AREA TO THE EAST THU 
NIGHT AS SPRAWLING CANADIAN HIGH PRESSURE FILLS IN FROM THE NW. LLVL 
PROFILES ALONG THE TENN BORDER INDICATE A LOW CHANCE OF LINGERING 
SNOW SHOWERS IN NW FLOW...BUT THIS DIMINISHES QUICKLY. GLOBAL MODELS 
NOW IN STRONG CONSENSUS THAT THE HIGH WILL CONTINUE TO PUSH THE 
FRONTAL BOUNDARY TO THE FLA PANHANDLE. DRY CONDITIONS WILL PREVAIL 
FRI-SAT AS A RESULT. MAX TEMPS 10 TO 15 DEGREES BELOW CLIMO FRIDAY 
BEFORE AIRMASS MODIFIES AND TOP OUT AROUND 5 BELOW CLIMO SATURDAY. 
HOWEVER COOL TEMPS ARE REINFORCED BY A SECOND COLD FRONT SATURDAY 
NIGHT. WHILE THE FROPA ITSELF APPEARS GENERALLY DRY EXCEPT POSSIBLY 
ALONG THE TENN BORDER...THE 02/00Z EC AND A HANDFUL OF NAEFS 
ENSEMBLE MEMBERS SUGGEST A WAVE COULD DEVELOP ALONG THE OLD 
STATIONARY FRONT OVER THE CENTRAL GULF STATES AND LIFT INTO THE AREA 
SUN OR SUN NIGHT. POPS WERE ALLOWED TO RAMP BACK UP FROM THE SW 
BEGINNING SUNDAY. TEMPS SUN NIGHT WILL BE COOL ENOUGH THAT A 
RAIN/SNOW MIX COULD RESULT OVER PARTS OF THE AREA. FURTHER 
MODERATION IN TEMPS IS IN STORE FOR MONDAY AS SKIES BEGIN TO CLEAR.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
AT KCLT...VFR EXPECTED INTO THE MIDDLE PART OF THE EVENING. THINK 
LOW CLOUDS WILL DEVELOP THIS AFTERNOON WITH BASES IN THE 035-050 
RANGE...WHICH COULD BRING A TEMPORARY CEILING. A WEST WIND AT THE 
MOMENT IS MOST LIKELY TO COME AROUND TO NW OR N. THE SITUATION 
SHOULD GO DOWNHILL THIS EVENING AS LOW LEVEL MOISTURE RETURNS ALONG 
WITH ISENTROPIC LIFT ABOVE A BACK DOOR COLD FRONT EXPECTED TO SLIP 
THROUGH FROM THE NE DURING THE EARLY EVENING. EXPECT AN MVFR CEILING 
TO DEVELOP NO LATER THAN 03Z...WHICH WILL EVENTUALLY LOWER TO IFR AS 
LIGHT PRECIP DEVELOPS AND UPGLIDE INCREASES IN THE PRE-DAWN HOURS. 
WINDS SHOULD BE NE FROM EARLY EVENING THROUGH THE END OF THE TAF 
PERIOD. THERE SHOULD BE SOME IMPROVEMENT TO CEILINGS...INTO THE 
LOWER PART OF MVFR...AROUND MID MORNING ON TUESDAY AS THE BOUNDARY 
LAYER WARMS.

ELSEWHERE...AN MVFR CEILING AT KAVL SHOULD BREAK UP DURING THE EARLY 
TO MID AFTERNOON. AFTER THAT...THE FCST WILL PROCEED SIMILAR TO KCLT 
WITH SOME MINOR TIMING DIFFERENCES. THE BACK DOOR FRONT SHOULD DROP 
DOWN TO THE S/SW ACROSS THE REGION IN THE EARLY TO MID EVENING... 
BRINGING THE WIND AROUND TO THE N/NE. CLOUDS DEVELOP IN THE MID 
EVENING AS THE FRONT GOES THROUGH...FIRST MVFR AND THEN IFR. A 
CONCERN WILL BE TEMPS IN THE PRE-DAWN THRU DAYBREAK HOURS. AT THIS 
TIME...IT APPEARS THAT ONLY KHKY HAS A CHANCE AT ANY FREEZING 
RAIN...AND THAT CHANCE SHOULD BE SMALL AS THE MAIN POTENTIAL IS 
ACTUALLY CLOSER TO THE BLUE RIDGE. 
  
OUTLOOK...LOW CIGS AND LIGHT PRECIP/DRIZZLE WILL BE LIKELY ACROSS 
MUCH OF THE AREA IN TUESDAY AFTERNOON AND EVENING. A COLD FRONT WILL 
MOVE SLOWLY THROUGH THE REGION WED THROUGH THURSDAY...BRINGING 
CHANCES FOR HEAVIER RAINFALL TO THE AREA. FRIDAY AND SATURDAY LOOK 
VFR.

CONFIDENCE TABLE...

            13-19Z        19-01Z        01-07Z        07-12Z 
KCLT       HIGH  95%     HIGH 100%     HIGH 100%     HIGH 100%     
KGSP       HIGH 100%     HIGH 100%     HIGH 100%     HIGH 100%     
KAVL       MED   74%     HIGH 100%     HIGH 100%     HIGH 100%     
KHKY       MED   77%     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...FREEZING RAIN ADVISORY FROM MIDNIGHT TONIGHT TO NOON EST 
     TUESDAY FOR NCZ033-049-050-501-503-505.
SC...NONE.

&&

$$
SYNOPSIS...CSH
NEAR TERM...PM/SBK
SHORT TERM...CDG
LONG TERM...WIMBERLEY
AVIATION...PM


National Weather Service
Weather Forecast Office Greenville-Spartanburg
GSP International Airport
1549 GSP Drive
Greer, SC 29651
(864) 848-3859
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Page last modified: January 20, 2010

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