339  
FXUS62 KGSP 200834  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
434 AM EDT WED AUG 20 2014  
   
SYNOPSIS
 
 
A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE WILL BUILD ACROSS THE  
MISSISSIPPI RIVER VALLEY OVER THE NEXT FEW DAYS AND LINGER FOR THE  
REST OF THE WORK WEEK...RESULTING IN ABOVE NORMAL TEMPERATURES. A  
WEAK COLD FRONT WILL THEN PUSH INTO THE AREA FROM NORTHEAST SATURDAY  
AND BRING SOME MINOR RELIEF FROM THE HEAT.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
0830 UTC UPDATED...POPS HAVE BEEN ADJUSTED PER RADAR TRENDS...WITH A  
DECREASE IN MOST PLACES...BUT AN INCREASE IN THE NW NC PIEDMONT  
WHERE A LIGHT SHOWER HAS DEVELOPED. SKY COVER WAS UPDATED FROM  
INFRARED SATELLITE IMAGERY.  
 
AT 300 AM EDT TUESDAY...AN UPPER TROUGH WILL AMPLIFY ALONG THE EAST  
COAST TODAY...WHILE AN UPPER RIDGE BUILDS NORTH OVER THE MS RIVER  
VALLEY. SEVERAL WEAK SHORTWAVES WILL CROSS OUR AREA TODAY AND  
TONIGHT IN NW FLOW ALOFT....WHILE A COLD FRONT ADVANCES SLOWLY FORM  
THE NE. IT IS UNCLEAR WHETHER THE FRONT WILL MAKE IT VERY FAR INTO  
OUR AREA...BUT ITS GENERAL PROXIMITY MAY FOCUS CONVECTION ACROSS OUR  
NORTHERN TIER OF COUNTIES. EVEN IF THE FRONT REMAINS OFF TO THE  
NORTHEAST...OUR AREA WILL BE IN A MOIST UNSTABLE AIR MASS...AND  
PASSING SHORTWAVES WILL PROVIDE SUPPORT FOR CONVECTION. MOISTURE  
WILL BE SOMEWHAT LIMITED...AND STEERING FLOW GREAT ENOUGH TO KEEP  
CELLS MOVING...LIMITING THE POTENTIAL FOR HEAVY RAINFALL. ROBUST  
CAPE WILL BE PRESENT...AND DRY AIR WILL BE AVAILABLE FOR EVAPORATIVE  
COOLING...PROVIDING SUPPORT FOR WIND GUSTS AND HAIL. HIGH  
TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL.  
 
SOME ELEVATED INSTABILITY WILL LINGER THROUGH TONIGHT...AND IF ANY  
MCS ROUNDING THE CORNER OF THE RIDGE REACHES OUR AREA...IT MAY WELL  
SURVIVE. STEERING FLOW AND A LACK OF DEEP MOISTURE WILL LIMIT HEAVY  
RAINFALL POTENTIAL. MINIMUM TEMPERATURES WILL RUN ABOVE NORMAL IN A  
MOIST AIRMASS.  
 

 
   
SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
 
 
AS OF 300 AM WEDNESDAY...A LARGE UPPER RIDGE WILL PERSIST ACRS THE  
LWR-MID MS VALLEY...EXTENDING EAST ACRS THE SOUTHEAST STATES THRU  
THE SHORT TERM. THE LATEST GUIDANCE SHOWS THAT A RING OF FIRE  
PATTERN WILL SET UP...WITH A SERIES OF SHORTWAVES AND ASSOCIATED  
CLUSTERS OF CONVECTION WILL RIDE OVER TOP OF THE RIDGE...FROM THE  
UPR MIDWEST/SRN GREAT LAKES...TO THE MID ATLANTIC. IT LOOKS LIKE  
MOST OF THE ASSOCIATED ACTIVITY WILL STAY NORTH OF THE CWFA.  
HOWEVER...THE NRN ZONES (GENERALLY I-40 CORRIDOR AND NORTH)...MAY  
GET BRUSHED BY A POSSIBLE MCS AT SOME POINT. NOT MUCH CHANGE WAS  
MADE TO THE POPS. STILL EXPECT AT LEAST A HANDFUL OF  
DIURNALLY-DRIVEN CONVECTION...AS STEEP MID LVL LAPSE RATES REMAIN  
ATOP THE REGION. MODELS ARE TRENDING WARMER FOR THURSDAY AND  
FRIDAY...SO I BUMPED UP TEMPS ABOUT A CATEGORY...EVEN MORE IN THE NW  
NC PIEDMONT...WHERE WE PREVIOUSLY THOUGHT A BACKDOOR COLD FRONT  
WOULD PUSH IN BY FRIDAY. THIS RESULTS IN ABOVE NORMAL TEMPS...WITH  
UPR 80S IN THE MTN VALLEYS AND MID-UPR 90S ACRS THE PIEDMONT.  
 

 
   
LONG TERM /SATURDAY THROUGH TUESDAY/
 
 
AS OF 315 AM WEDNESDAY...THE UPPER FLOW LOOKS TO BECOME MORE  
NORTHERLY ATOP THE CWFA FOR SATURDAY AND SUNDAY...AS RIDGE AXIS  
DRIFTS SLIGHTLY EAST...WHILE A LARGE TROF REMAINS NEARLY STATIONARY  
JUST OFF THE EAST COAST. WHILE THE MEDIUM RANGE GUIDANCE HAS DELAYED  
THE TIMING OF A BACKDOOR COLD FRONTAL PASSAGE BY A FULL DAY...THEY  
STILL SHOW IT COMING THRU...WITH SLIGHTLY COOLER TEMPS AND INCREASED  
CHC FOR PRECIP. BOTH THE 00Z/20 GFS AND ECMWF SHOW WEDGE-LIKE  
CONFIGURATION FOR SUNDAY...WITH A 1021-1023 MB SFC HIGH OVER THE  
CANADIAN MARITIMES...NOSING A RIDGE AXIS SW ALONG THE EAST COAST.  
LIGHT NELY LLVL FLOW AND INCREASED CLOUDS SHUD KEEP TEMPS CLOSER TO  
NORMAL...ESP SUNDAY.  
 
FOR MONDAY AND TUESDAY...THE SFC HIGH SINKS SOUTHWARD...KEEPING  
COOLER LLVL THICKNESSES ACRS THE REGION...AND CONTINUED LIGHT ELY  
LLVL FLOW. I WILL FCST TEMPS BACK TO NORMAL...EVEN SLIGHTLY BELOW  
NORMAL IN THE NW NC PIEDMONT...WITH CONTINUE SLGT CHC TO CHC POPS.  
 

 
   
AVIATION /09Z WEDNESDAY THROUGH SUNDAY/
 
 
AT KCLT...RAIN EARLIER TODAY WILL FAVOR FOG FORMATION BY DAWN. MVFR  
CIG AND VSBY WILL BE INTRODUCED BEFORE DAYBREAK. MODEL TIME HEIGHTS  
SHOW LOW VFR CLOUDS LINGERING THROUGH THE FORECAST. ALTHOUGH A COLD  
FRONT WILL APPROACH FORM THE NE OVERNIGHT...IT IS UNCLEAR IF THE  
FRONT WILL REACH KCLT OR NOT...AND SERVE AS A FOCUSING MECHANISM FOR  
BOTH CLOUDS AND CONVECTION. CURRENTLY...VERY LITTLE CLOUD COVER IS  
ASSOCIATED WITH THIS BOUNDARY. AT THIS TIME GUIDANCE VEERS WINDS  
FROM SW TO NE OVERNIGHT...THEN BACKS THEM TO SW TODAY...AND ONLY  
VEERS THEM NW TONIGHT. CONVECTIVE CHANCES ARE TOO LOW TO WARRANT A  
MENTION IN THE TAF THIS AFTERNOON...AND LOW VFR CIGS WILL NOT BE  
CARRIED WITHER.  
 
ELSEWHERE...GUIDANCE FAVORS FOG AT DAYBREAK...BUT MAY BE TOO  
AGGRESSIVE. FOR NOW DAYBREAK MVFR VSBY AND CIGS WILL BE CARRIED AT  
ALL SITES BUT KGMU. WINDS VEER FROM SW TO NE OVERNIGHT AS A COLD  
FRONT APPROACHES FORM THE NE...BUT NEVER VEER NE AT ANY TAF SITES.  
WINDS BACK TO SW TODAY...THEN VEER NW TONIGHT. THE PROXIMITY OF THIS  
FRONT COULD SERVE AS A FOCUSING MECHANISM FOR CLOUDS AND CONVECTION  
DURING THE DAY...BUT AT THIS TIME LITTLE CLOUDS COVER WAS NOTED WITH  
THIS FEATURE. AFTERNOON CONVECTION WILL BE FEATURED AT KAVL ONLY...  
WITH LOW VFR CIGS AND VSBY CARRIED WITH CONVECTION.  
 
OUTLOOK...SCT AFTERNOON CONVECTION AND PATCHY EARLY MORNING FOG WILL  
REMAIN IN THE FORECAST THROUGH THE WEEK. THERE WILL ALSO BE  
INCREASING CHANCES FOR REMNANT ORGANIZED CONVECTION APPROACHING THE  
AREA FROM THE NW DURING THE LATE NIGHT/EARLY MORNING HOURS.  
 
CONFIDENCE TABLE...  
 
08-14Z 14-20Z 20-02Z 02-08Z  
KCLT MED 71% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 87% HIGH 100% HIGH 100% HIGH 100%  
KAVL HIGH 94% HIGH 100% HIGH 100% HIGH 100%  
KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGMU HIGH 91% 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...ARK  
NEAR TERM...JAT  
SHORT TERM...ARK  
LONG TERM...ARK  
AVIATION...JAT  
 
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