379  
FXUS62 KGSP 010554  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
154 AM EDT WED OCT 1 2014  
   
SYNOPSIS
 
 
DRIER HIGH PRESSURE WILL LINGER OVER THE REGION THROUGH THURSDAY. A  
COLD FRONT WILL THEN ARRIVE FROM THE NORTHWEST ON FRIDAY AND MOVE  
OFFSHORE BY EARLY SATURDAY. IN THE FRONTS WAKE...A COOL AND DRY  
AIRMASS WILL MOVE BACK OVER THE SOUTHEAST AND REMAIN IN PLACE OVER  
THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH TODAY/
 
 
AS OF 130 AM...THE FCST APPEARS TO BE ON TRACK. TEMP/RH TRENDS LOOK  
GOOD. WILL CONTINUE TO MONITOR FOG DEVELOPMENT. NO SIGNIFICANT  
CHANGES.  
 
REMAINDER OF PREVIOUS DISCUSSION...  
SHUD SEE PATCHY FOG THOUGH...ESPECIALLY NEAR BODIES OF WATER. FCST  
STILL LOOKS GOOD FOR DENSE MTN VALLEY FOG OVERNIGHT...SO HAVE ADDED  
THAT TO THE FCST.  
 
A CLOSED UPPER LOW WILL MOVE FROM THE EASTERN GREAT LAKES TO  
SOUTHERN NEW ENGLAND BY WEDNESDAY EVENING...WHILE THE TROUGH TO ITS  
SOUTH DEAMPLIFIES. MEANWHILE...AN UPPER RIDGE AXIS WILL PROGRESS  
FORM THE MS RIVER VALLEY TO THE OH AND TN RIVER VALLEYS. A COLD  
FRONT NOW IN THE OH RIVER VALLEY WILL STALL TO OUR NORTH...WHILE  
WEAK HIGH PRESSURE REMAINS OVER THE CAROLINAS AND GA.  
 
WEDNESDAY FEATURES CONDITIONS MUCH LIKE TUESDAY...WITH SOME  
SCATTERED LOW CLOUDS AND A CAPPING INVERSION ABOVE. THE ONE CAVEAT  
WOULD BE IF THE FRONT TO THE NORTH CAN DROP INTO THE INTERSTATE 40  
CORRIDOR BEFORE STALLING...WHICH WOULD RESULT IN A FEW MORE CLOUDS  
AND A WIND SHIFT FROM LIGHT SW TO LIGHT NE. TEMPERATURES ARE  
EXPECTED TO RUN A FEW DEGREES ABOVE NORMAL AS HEIGHTS SLOWLY RISE  
ALOFT.  
 

 
   
SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/
 
 
AS OF 215 PM TUESDAY...AN UPPER RIDGE AXIS WILL REMAIN ACRS THE CWFA  
ON THURSDAY...KEEPING THE AREA DRY WITH ABOVE NORMAL TEMPS.  
 
HEIGHTS BEGIN TO FALL IN EARNEST THURSDAY NIGHT...AS A POTENT  
SHORTWAVE TROF DIVES INTO THE MIDWEST. IN THE LLVLS...S/SWLY FLOW  
WILL INCREASE...TRANSPORTING GULF MOISTURE INTO THE AREA. THERE MAY  
BE SOME UPSLOPE-ENHANCED SHOWER ACTIVITY DEVELOPING OVERNIGHT  
THURSDAY NIGHT IN THE WESTERN ZONES. OTHERWISE...SHUD BE GENERALLY  
DRY WITH INCREASING RETURN FLOW AND CLOUD COVER...TEMPS WILL BE WELL  
ABOVE NORMAL...MAINLY IN THE 60S.  
 
MODELS ARE STILL IN GOOD AGREEMENT ON THE TIMING OF A COLD FRONT TO  
CROSS THE AREA ON FRIDAY. A PRE-FRONTAL BAND OF CONVECTION IS LIKELY  
TO CROSS THE AREA DURING THE DAYLIGHT HOURS...WITH THE SFC FRONT  
COMING THRU FRIDAY EVENING. AS AN 500 MB LOW CLOSES OFF INVOF MN...A  
VORT LOBE SHUD LIFT NE ACRS THE SRN APPALACHIANS...PROVIDING  
DEEP-LAYER Q-VECTOR CONVERGENCE. GUIDANCE ALSO SHOWS PLENTY OF UPPER  
DIVERGENCE WITH THE BAND OF PRECIP. SO CONFIDENCE IS INCREASING ON  
THE POP FOR FRIDAY. I HAVE CATEGORICAL POP IN THE MTNS AND LIKELY  
ACRS THE PIEDMONT...THEN TAPERING OFF FRIDAY NIGHT.  
 
AS FOR HOW ROBUST THE CONVECTION WILL BE...THERE LOOKS TO BE ABOUT  
1000-1500 J/KG OF SBCAPE FOR THE LINE TO WORK WITH...WITH 0-6 KM  
BULK SHEAR OF 40-50 KTS. CERTAINLY ENUF FOR AT LEAST A LOW-TOPPED  
QUASI-LINEAR CONVECTIVE SYSTEM (QLCS). WE ARE NOT CURRENTLY  
MENTIONING SEVERE WX IN THE HWO...BUT I WOULDN/T BE SURPRISED IF SPC  
PLACES SOME AREA IN A SLGT FOR THE NEW DAY 3 TONIGHT FOR FRIDAY...IF  
MODEL TRENDS HOLD.  
 
TEMPS WILL BE NEAR OR SLIGHTLY BELOW NORMAL FRIDAY AND FRIDAY NIGHT  
WITH THE PRECIP...AND PASSING COLD FRONT.  
 

 
   
LONG TERM /SATURDAY THROUGH TUESDAY/
 
 
AS OF 150 PM TUESDAY AFTERNOON...THE MEDIUM RANGE FCST PICKS UP AT  
12Z ON SATURDAY WITH A STEEP UPPER TROF TO OUR NORTH AND BROAD UPPER  
RIDGING BUILDING OVER THE WEST COAST. AS WE MOVE INTO THE LATTER  
PART OF THE WEEKEND...THE TROF AXIS LIFTS NE YET WE LIKELY WILL  
REMAIN UNDER BROAD UPPER TROFFING THRU THE END OF THE PERIOD. THE  
ECMWF CONTINUES TO REAMPLIFY THE TROF MORE THAN THE GFS ON DAYS 6  
AND 7 WITH CONSIDERABLY LOWER HEIGHTS OVER THE FCST AREA ON NEW DAY  
7...TUES. THE LATEST GFS DEVELOPS A VERY LARGE CLOSED H5 LOW OVER  
ONTARIO AND THUS MAINTAINS A MUCH LONGER WAVELENGTH TROF THRU NEW  
DAY 7.  
 
AT THE SFC...IN THE WAKE OF THE FROPA ON FRI AFTERNOON AND  
EVENING...COOL AND DRY HIGH PRESSURE WILL SPREAD OVER THE CWFA AND  
REMAIN THRU THE WEEKEND. THE MODELS CONTINUE TO DEVELOP SOME SORT OF  
GREAT LAKES LOW EARLY NEXT WEEK AND MOVE A SECOND COLD FRONT OVER  
OUR AREA. THE GFS HAS THE FROPA ON MON WHILE THE ECMWF IS ABOUT 24  
HRS SLOWER WITH THE FROPA ON TUES. BOTH MODELS SUGGEST A FAIRLY  
QUICK AND MOSTLY DRY FROPA WITH LITTLE IN THE WAY OF QPF. AS FOR THE  
SENSIBLE FCST...WE CAN EXPECT MOSTLY DRY AND COOL CONDITIONS THRU  
THE PERIOD WITH JUST SOME SLIGHT CHANCE POPS ON MON AFTERNOON THRU  
TUES TO ACCOUNT FOR THE NEXT FROPA. TEMP GUIDANCE HAS BEEN TRENDING  
COOLER WITH HIGHS IN THE UPPER 60S TO LOW 70S OVER THE WEEKEND AND  
WARMING BETWEEN 1 AND 2 CATEGORIES EARLY NEXT WEEK.  
 

 
   
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
 
 
AT KCLT...FOG WAS GRADUALLY DEVELOPING ACROSS PARTS OF THE NC  
PIEDMONT AS OF 06Z. THINK THAT EVENTUALLY THE MVFR VISIBILITY WILL  
SURROUND KCLT AND WILL PROBABLY BE IFR/LIFR AT OUTLYING SPOTS.  
HOWEVER...EXPECT KCLT TO BE SLOW TO SEE FOG DEVELOPMENT. DEWPT  
DEPRESSION REMAINS 3 DEGREES ON THE MOST RECENT OBSERVATION. WILL  
ADD A TEMPO PERIOD OF MVFR FOG IN THE 09Z-13Z TIME FRAME. IF  
OBSERVATIONS DROP TO MVFR...THEN IFR WILL BE A DISTINCT POSSIBILITY  
AND THE TAF WILL BE AMENDED TO INCLUDE THAT IN A TEMPO. THE FOG  
SHOULD BURN OFF QUICKLY ONCE AGAIN. FROM MID MORNING ONWARD...EXPECT  
FEW/SCT STRATOCU WITH BASES AROUND 050 AND A LIGHT S/SW WIND. KEPT  
THOSE CONDITIONS THROUGH THE END OF THE CURRENT PERIOD.  
 
ELSEWHERE...SIMILAR CONDITIONS AS KCLT...ESP KGSP/KGMU. KHKY/KAND  
SHUD SEE MVFR FOG OVERNIGHT...WITH LITTLE TO NO CHC OF LOW CLOUDS.  
KAVL THE MAJOR EXCEPTION...AS USUAL...WITH ANOTHER ROUND OF VLIFR  
POSSIBLE. SHOULD BE A QUICK RETURN TO VFR BY MID MORNING...WITH  
CONVECTIVE CU DEVELOPING ONCE AGAIN ALL AREAS. LIGHT WIND BECOMES  
CALM OVERNIGHT THEN SSW WED AFTERNOON. KAVL WILL SEE AN UPVALLEY  
WIND DURING THE MORNING AND INTO THE AFTERNOON...BECOMING DOWNVALLEY  
IN THE LATE AFTERNOON AND EVENING.  
 
OUTLOOK...FOG/VSBY CONCERNS REMAIN EARLY THURSDAY MORNING. A FRONT  
WILL APPROACH ON FRIDAY WHICH COULD TRIGGER SOME SHOWERS AND  
THUNDERSTORMS...WITH ASSOCIATED RESTRICTIONS POSSIBLE...AS IT MOVES  
ACROSS THE REGION FRIDAY AFTERNOON AND NIGHT. VFR RETURNS ON  
SATURDAY THROUGH THE REST OF THE WEEKEND.  
 
CONFIDENCE TABLE...  
 
06-12Z 12-18Z 18-24Z 00-06Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAVL MED 72% MED 79% 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...JAT/PM/RWH  
SHORT TERM...ARK  
LONG TERM...JPT  
AVIATION...PM  
 
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