278  
FXUS62 KGSP 180011  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
811 PM EDT TUE JUL 17 2018  
   
SYNOPSIS
 
 
A WEAK SURFACE COOL FRONT WILL SLOWLY CROSS OUR AREA FROM THE  
NORTHWEST AND SHOULD BE ALONG THE CAROLINA COAST BY WEDNESDAY  
MORNING. THE FRONT WILL SETTLE JUST SOUTH OF THE AREA ON WEDNESDAY  
WHILE HIGH PRESSURE BUILDS DOWN FROM THE NORTH FOR THE LATTER HALF  
OF THE WEEK. ANOTHER COLD FRONT WILL APPROACH FROM THE WEST AND MOVE  
SLOWLY ACROSS THE AREA OVER THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY/
 
 
AS OF 800 PM...A COUPLE CLUSTERS OF SCATTERED THUNDERSTORMS CONTINUE  
TO WORK THEIR WAY SOUTH THROUGH THE UPSTATE AND NE GA, WHICH  
CONVECTION TO THE NORTH CLOSER TO A SOUTHWARD-MOVING FRONT STRUGGLE  
TO GET GOING. POPS WERE ADJUSTED TO MAINLY FAVOR THE SOUTHERN PART  
OF THE FORECAST AREA. THE FRONT WILL PUSH THRU LATER THIS EVENING,  
BUT THE CAMS ARE NOT THAT IMPRESSED WITH CONVECTION RE-FIRING ALONG  
THE BOUNDARY. SEVERE THREAT SEEMS TO BE MAINLY CONFINED TO THE UPPER  
SAVANNAH VALLEY, WHERE CAPE IS STILL OVER 2500 J/KG WITH DCAPE IS  
800-1400 J/KG PER THE LATEST SPC MESOANALYSIS. CONDITIONS SHOULD  
WIND DOWN THRU THE EVENING.  
 
THE COLD FRONT MOVES SOUTH OF THE AREA OVERNIGHT TAKING THE  
CONVECTION WITH IT. THERE MAY BE SOME PATCHY FOG OR LOW CLOUDS IN  
THE MOUNTAIN VALLEYS BUT DENSE FOG NOT EXPECTED. LOWS WILL BE A  
LITTLE ABOVE NORMAL. DRIER HIGH PRESSURE BUILDS IN FROM THE NORTH ON  
WEDNESDAY. THERE MAY BE ENOUGH LINGERING LOW LEVEL MOISTURE FOR  
ISOLATED CONVECTION ACROSS THE FAR SOUTHERN CWFA OR SOUTHWESTERN NC  
MOUNTAINS. HOWEVER, CHANCE IS QUITE LOW, SO HAVE KEPT THE FORECAST  
DRY FOR NOW. HIGHS WILL BE NEAR NORMAL WITH LOWER HUMIDITY VALUES  
THAN THE PAST FEW DAYS.  
 

 
   
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
 
 
AS OF 255 PM EDT TUESDAY: THE SHORT TERM FORECAST PERIOD KICKS OFF  
WEDNESDAY NIGHT AS LATEST GUIDANCE CONTINUES TO PLACE A RECENTLY  
PASSED COLD FRONT JUST SOUTH OF THE FA WHERE IT IS EXPECTED TO  
STALL, WITH SFC HIGH PRESSURE BUILDING IN BRINGING A DRIER, THOUGH  
NOT SIGNIFICANTLY COOLER, AIRMASS. THIS WILL RESULT IN FAIRLY QUIET  
CONDITIONS WEDNESDAY NIGHT AS LOW TEMPERATURES DROP INTO THE LOWER  
70S ALONG AND SOUTH OF THE I-85 CORRIDOR, COOLER INTO THE 60S BACK  
ACROSS THE MOUNTAINS.  
 
AS THE SFC HIGH MOVES ACROSS THE OH VALLEY AND EAST-NORTHEAST AS IT  
BEGINS TO WEDGE BACK IN ACROSS THE AREA ON THURSDAY, UPPER TROUGH  
ACROSS NE WILL PUSH EASTWARD AS UPPER RIDING CONTINUES TO BUILD IN  
FROM THE WEST. THIS SHIFT IN THE SYNOPTIC PATTERN WILL ALLOW FOR LOW-  
LEVEL FLOW TO BECOME EASTERLY, WHICH WITH THE AID OF  
UPSLOPE/CONVERGENCE, COULD AID IN THE DEVELOPMENT OF ISOLATED  
SHOWERS AND THUNDERSTORMS MAINLY ACROSS THE MOUNTAINS THURSDAY  
AFTERNOON AND EVENING. AS INSTABILITY REMAINS FAIRLY WEAK, DO NOT  
ANTICIPATE ANY SEVERE WEATHER ATTM. HIGH TEMPERATURES ON THURSDAY  
WILL HOVER JUST AT OR SLIGHTLY BELOW NORMAL.  
 
INTO FRIDAY, SFC HIGH IS PROGGED TO PUSH FURTHER OFF TO THE  
NORTHEAST FROM THE EAST COAST WITH UPPER RIDGE QUICKLY PUSHING OFF  
TO THE EAST AS WELL, AS AN UPPER LOW MOVES INTO THE MIDWEST. SOME  
GUIDANCE HINTS AT THE POSSIBILITY OF A PIECE OF ENERGY FROM THIS  
FEATURE MOVING OVERHEAD FROM THE UPPER LOW INTO FRIDAY NIGHT AHEAD  
OF THE APPROACHING TROUGH AXIS, THOUGH OTHER GUIDANCE SUGGESTS IT  
HOLDS OFF FROM REACHING THE AREA UNTIL JUST BEYOND THE SHORT TERM  
FORECAST PERIOD. AT THE SAME TIME, INTEREST REMAINS ON THE STALLED  
FRONT TO SOUTH WHERE GUIDANCE SUGGESTS A COASTAL LOW FORMING NEAR  
THE GA/SC COAST, WHICH WILL GRADUALLY BEGIN TO LIFT TOWARDS THE FA  
TOWARDS THE END OF THE FORECAST PERIOD. IN BETWEEN ALL THESE  
FEATURES AND INCREASING LOW LEVEL MOISTURE FROM THAT IN PLACE ON  
THURSDAY, ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL BE  
POSSIBLE ON FRIDAY, WITH HIGHER CHANCES CONFINED TO THE TN/NC BORDER  
AND LOWER CHANCES EASTWARD BACK TOWARDS THE I-77 CORRIDOR.  
TEMPERATURES THURSDAY NIGHT AND FRIDAY WILL BE AROUND NORMAL.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 215 PM EDT TUESDAY: STARTING 00Z SATURDAY. HEIGHTS WILL BE  
FALLING AS THE UPPER TROUGH DIPS DOWN FROM THE GREAT LAKES WITH THE  
UPPER LOW OVER EASTERN KENTUCKY AND OHIO SATURDAY NIGHT. THE UPPER  
LOW OPENS UP LATE SUNDAY AND SUNDAY NIGHT WITH THE UPPER TROUGH WITH  
AXIS FROM THE FLORIDA PENINSULA TO CLEVELAND BEGINS TO WEAKEN AND  
PULLS OUT TO THE EAST. THE TROUGH CONTINUES TO BREAK DOWN THROUGH  
TUESDAY BEFORE THE NEXT TROUGH MOVES SE FROM THE UPPER PLAINS.  
 
AT THE SURFACE, HIGH PRESSURE PULLS OUT TO THE EAST OF NEW ENGLAND  
ON SATURDAY WITH A WARM FRONT MOVING FROM SC TO VA AND COLD FRONT  
CROSSING EASTERN TN. CAPE VALUES FROM 2500 TO 3500 FROM ATLANTA TO  
BIRMINGHAM TO CHATTANOOGA AREA 2 PM SATURDAY FADE AS THIS MOVES  
ACROSS NORTH GA TO SC INTO THE EVENING GIVING THE ENERGY FOR STRONG  
CONVECTION WITH POSSIBLE SVRS ACROSS THE UPPER SAVANNAH VALLEY.  
PRECIPITABLE WATER VALUES NEAR 2 INCHES OVER THE GA AND SC PIEDMONT  
LATE SATURDAY WILL CONTRIBUTE TO HIGH RAIN RATES WITH THE  
CONVECTION. FORECAST IS MUCH MORE STABLE OVER WESTERN NC LATE  
SATURDAY. THE FRONT MOVES TO THE EASTERN PIEDMONT AND MIDLANDS TO  
SANDHILLS BY SUNDAY NIGHT. ALTHOUGH CAPE WILL BE MUCH LOWER TO START  
THE NEW WEEK, CONSIDERATION MUST BE GIVING TO COOLER TEMPERATURES IN  
THE MID AND UPPER LEVELS WITHIN THE TROUGH. MAX TEMPERATURES ABOUT  
A CATEGORY BELOW NORMAL WILL RECOVER ON TUESDAY TO NEAR NORMAL AS  
THE TROUGH DEPARTS.  
 

 
   
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
 
 
AT KCLT AND ELSEWHERE: CONVECTION MAINLY CONFINED TO THE UPSTATE,  
WITH A FEW SHOWERS TRYING TO DEVELOP ALONG A COLD FRONT ACROSS THE  
I-40 CORRIDOR. CONFIDENCE IS BELOW AVERAGE FOR CONVECTION IMPACTING  
KCLT. THE LATEST HIGH-RES GUIDANCE SHOWS VERY LITTLE ADDITIONAL  
STORMS IN THE AREA, SO HAVE OPTED TO CARRY NO TEMPO THIS EVENING.  
BUT THERE IS STILL A SMALL CHANCE SOMETHING COULD TRIGGER. FOR THE  
UPSTATE SITES, STORMS ARE DRIFTING SOUTH OF GMU/GSP, WHERE VCTS WILL  
BE CARRIED, AND A TEMPO AT KAND, WHICH IN DIRECT PATH. BY AROUND  
3-4Z, THINGS SHOULD BE WINDING DOWN, LEAVING JUST MID-LEVEL CIGS AND  
SOME PATCHY MOUNTAIN VALLEY FOG. THE COLD FRONT WILL PUSH THRU AND  
TURN WINDS AROUND OUT OF THE N TO NE OVERNIGHT, PERSISTING OUT OF  
THE NE ON WEDNESDAY. HIGH PRESSURE BUILDING IN FROM THE NORTH WILL  
BRING SLIGHTLY DRIER AIR, AND SHOULD KEEP ALL DEEP CONVECTION OFF TO  
THE SOUTH.  
 
OUTLOOK: DRIER/MORE STABLE AIR FILTERING INTO THE AREA SHOULD RESULT  
IN LESS COVERAGE OF AFTERNOON/EVENING SHOWERS AND STORMS THURSDAY.  
EXPECT TYPICAL SUMMERTIME CONDITIONS TO RETURN FOR LATE WEEK. FOG  
AND/OR LOW STRATUS WILL BE POSSIBLE MOST MORNINGS, PARTICULARLY OVER  
THE MTN VALLEYS.  
 
CONFIDENCE TABLE...  
 
00-06Z 06-12Z 12-18Z 18-00Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAVL HIGH 100% LOW 58% HIGH 98% HIGH 100%  
KHKY HIGH 95% MED 79% HIGH 100% HIGH 100%  
KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAND HIGH 100% HIGH 95% 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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

 
   
GSP WATCHES/WARNINGS/ADVISORIES
 
 
GA...NONE.  
NC...NONE.  
SC...NONE.  
 

 
 

 
SYNOPSIS...DEO  
NEAR TERM...ARK/RWH  
SHORT TERM...SGL  
LONG TERM...DEO  
AVIATION...ARK  
 
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