251  
FXUS62 KGSP 142338  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
738 PM EDT TUE AUG 14 2018  
   
SYNOPSIS
 
 
AN UPPER-LEVEL TROUGH WILL MOVE AWAY FORECAST AREA ALLOWING RIDGING  
TO DEVELOP AND KEEPING CONDITIONS MOSTLY DRY THROUGH WEDNESDAY.  
MOISTURE LEVELS WILL BEGIN TO INCREASE THURSDAY CONTINUING INTO THE  
WEEKEND, AS ANOTHER UPPER LEVEL SYSTEMS BEGINS TO IMPACT THE AREA.  
 

 
   
NEAR TERM /THROUGH WEDNESDAY/
 
 
AS OF 730 PM: NO MAJOR CHANGES TO THE PUBLIC FCST WITH THIS UPDATE;  
MINOR CHANGES TO SKY/WIND FOR AVIATION UPDATE. MID AND UPPER-LEVEL  
HEIGHTS WILL RISE FROM THE WEST TONIGHT THROUGH WEDNESDAY. JUST A  
FEW MID OR HIGH CLOUDS LINGER OVERNIGHT. ANOTHER ROUND OF MOUNTAIN  
VALLEY FOG AND LOW CLOUDS WILL BE POSSIBLE DURING THE EARLY  
MORNING HOURS, BECOMING LOCALLY DENSE IN THE SOUTHWEST MOUNTAIN  
VALLEYS. THOUGH OVERALL EXPECTATIONS ARE THE SAME, MINOR TWEAKS TO  
THE TIMING/EXTENT OF FOG HAVE BEEN MADE. SOME MID-LEVEL MOISTURE  
MAY SNEAK IN UNDER THE RIDGE TO INCREASE CLOUD COVER A BIT WEDNESDAY  
AFTERNOON, BUT THIS SHOULD NOT INHIBIT HEATING FOR THE BULK OF THE  
DAY. 850 MB FLOW WILL BACK A BIT ON WEDNESDAY TO YIELD A SLIGHT  
UPTICK IN LOW LEVEL MOISTURE. INSTABILITY WILL BE QUITE MODEST,  
WITH LESS CAPPING OVER THE MOUNTAINS. COVERAGE OF AFTERNOON SHOWERS  
AND THUNDERSTORMS WILL INCREASE A BIT ABOVE TUESDAY COVERAGE, WITH  
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS MAINLY OVER THE  
HIGHER TERRAIN. MAXIMUM AND MINIMUM TEMPERATURES WILL RUN ABOUT  
ONE CATEGORY ABOVE CLIMO.  
 

 
   
SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/
 
 
AS OF 2:30 PM EDT TUESDAY: THE UPPER LEVEL RIDGE WILL BE EAST OF OUR  
FORECAST AREA (FA) WEDNESDAY NIGHT. THE FIRST SLUG OF MOISTURE WILL  
INFLUENCE OUR MOUNTAIN LOCATIONS WITH A FEW SHOWERS OR THUNDERSTORMS  
WEDNESDAY EVENING. THIS IS TIED INTO THE FIRST INFLUX OF MOISTURE  
WORKING ON THE MECHANICAL LIFT OF THE WEST FACING SLOPES. ONCE THE  
ATMOSPHERE IS WORKED OVER, ANY LINGERING SHOWERS SHOULD END. THE  
REMAINDER OF OUR FORECAST AREA WILL BE DRY.  
 
IT APPEARS THE GUIDANCE IS LATCHING ONTO THE IDEA OF DRAWING BACK  
POPS FOR THURSDAY. THERE SHOULD BE AN INCREASE IN MOISTURE, AND  
PROBABLY SOME CHAOTIC SURFACE PRESENTATION, BUT LITTLE IN THE WAY OF  
FORCING. THE ATMOSPHERE INSTABILITY WILL STILL BE RESPECTABLE WITH  
CAPES AROUND 1500 J/KG. WE KEPT POPS IN THE CHANCE CATEGORY WEST AND  
SLIGHT CHANCE EAST, BASED ON LATEST GUIDANCE.  
 
AS WE WORK INTO THURSDAY EVENING, IT IS DIFFICULT TO FIND ANY  
PARTICULAR FORCING PARAMETER FOR POPS, SO WE ENDED MOST EXCEPT IN  
THE MOUNTAINS.  
 
FRIDAY OFFERS A CHANGE WITH THE APPROACH OF THE UPPER TROUGH,  
ALTHOUGH IT IS DEAMPLIFYING AS IT IS UNDERCUT BY THE THE WESTERN END  
OF THE BERMUDA HIGH. NEVERTHELESS, A PACKET OF ENERGY SLIPPING  
ACROSS OUR FA FRIDAY, ALONG WITH SURFACE FRONTAL CONVERGENCE, AND AN  
UNSTABLE ATMOSPHERE SHOULD DO THE TRICK TO IGNITE SHOWERS AND  
THUNDERSTORMS. WE BROUGHT VALUES INTO THE LOW LIKELY RANGE IN THE  
WEST AND ABOUT MEDIUM ELSEWHERE. PRECIPITABLE WATER VALUES WILL BE  
EDGING UP TO 2.00 INCHES, THEREFORE LOCALLY HEAVY RAIN NOT OUT OF  
THE QUESTION.  
 
IN THE TEMPERATURE DEPARTMENT SINCE WE WENT LOWER ON POPS IN THE  
PIEDMONT AREAS, WE ARE A LITTLE HIGHER ON TEMPERATURES FOR THURSDAY.  
OTHERWISE ABOUT IN LINE WITH GUIDANCE FOR FRIDAY ACROSS THE BOARD.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 215 PM EDT TUESDAY: A BROAD MEAN TROUGH WILL BE IN PLACE  
ACROSS THE OHIO AND TENNESSEE VALLEYS OVER THE WEEKEND. SEVERAL  
DISTURBANCES WILL MOVE THROUGH THE MEAN FLOW LEADING TO SCATTERED  
SHOWERS AND THUNDERSTORMS ACROSS THE FORECAST AREA. RIDGING WILL  
BUILD ACROSS THE SOUTHEAST EARLY NEXT WEEK AS A DEEPER TROUGH  
DEVELOPS OVER THE MIDDLE OF THE COUNTRY. THE COVERAGE OF STORMS  
SHOULD BE A LITTLE LESS EARLY NEXT WEEK, BUT WILL NEED TO MAINTAIN  
RAIN CHANCES THROUGH THE PERIOD. TEMPERATURES THROUGH THE EXTENDED  
PERIOD ARE EXPECTED TO BE CLOSE TO CLIMO.  
 

 
   
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
 
 
AT KCLT AND ELSEWHERE: A RIDGE OF HIGH PRESSURE WILL SPREAD INTO  
THE AREA FROM THE WEST OVERNIGHT. THIS WILL LEAD TO MOSTLY CLEAR  
SKIES AND LIGHT WINDS IN THE EARLY MORNING; SOME FOG WILL FORM  
IN THE MOUNTAIN VALLEYS (INCL. KAVL) AS A RESULT. GUIDANCE DOES  
STRONGLY SUPPORT VFR PERSISTING AT THE REST OF THE TAF SITES,  
HOWEVER. WINDS WILL TEND TOWARD N TO NE AS DECOUPLING OCCURS BY  
LATE EVENING, BUT WILL GO CALM IN MANY LOCATIONS OVERNIGHT. THEY  
WILL PICK BACK UP FROM THE SW BY MIDDAY. CHANCES FOR SHRA/TSRA DO  
EXIST OVER THE MOUNTAINS WED AFTN, OTHERWISE BEING SUPPRESSED BY  
THE RIDGE. THE CHANCE STILL IS TOO LOW TO MENTION AT KAVL.  
 
OUTLOOK: INCREASING COVERAGE OF DIURNAL THUNDERSTORMS WILL DEVELOP  
FROM THURSDAY THROUGH THE UPCOMING WEEKEND. RESTRICTIONS WILL BE  
LIMITED MAINLY TO AREAS IN HEAVY SHOWERS AND LOWER RESTRICTIONS  
ACROSS THE MOUNTAIN VALLEYS EACH MORNING.  
 
CONFIDENCE TABLE...  
 
23-05Z 05-11Z 11-17Z 17-18Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAVL HIGH 100% HIGH 100% MED 61% HIGH 100%  
KHKY HIGH 100% HIGH 100% MED 75% 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:  
 
WWW.WEATHER.GOV/GSP/AVIATION  
 

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

 
 

 
SYNOPSIS...SW  
NEAR TERM...HG/WIMBERLEY  
SHORT TERM...TS  
LONG TERM...SW  
AVIATION...WIMBERLEY  
 
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