116  
FXUS62 KGSP 191450  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
1050 AM EDT SAT AUG 19 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD ACROSS THE FORECAST AREA AND BRING  
RELATIVELY DRIER CONDITIONS OVER THE WEEKEND. A WARMING AND  
MOISTENING AIRMASS WILL RETURN MONDAY BEFORE COOL DRY AIR WORKS IN  
BEHIND A FRONTAL PASSAGE WED NIGHT.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1030 AM EDT SATURDAY: STILL HAVE SOME MID-LEVEL CLOUDINESS  
OVER THE AREA BEHIND THE FRONT, AND A LITTLE BIT OF CU OVER THE  
MOUNTAINS, BUT OTHERWISE A VERY PLEASANT MORNING OUT THERE.  
DEWPOINTS ARE DROPPING BEHIND THE FRONT AND THE DIURNAL RISE IN  
TEMPERATURES IS A BIT SLOWER THAN FORECAST, SO HAVE MADE SEVERAL  
ADJUSTMENTS TO HOURLY TEMPERATURES. TWEAKED AFTERNOON HIGHS A BIT  
BUT RESULT ISN'T MUCH DIFFERENT THAN WHAT WE HAD BEFORE. POP  
FORECAST (WELL, LACK THEREOF) LOOKS GOOD. SHOULD BE A REALLY NICE  
SATURDAY ACROSS THE AREA.  
 
OTHERWISE, HEIGHTS WILL FALL SLIGHTLY TODAY, AS A SHORT WAVE TROUGH  
PASSES NORTH OF THE REGION. ASSOCIATED WEAK FRONTAL ZONE WILL  
CONTINUE TO OOZE SOUTHEAST OF THE FORECAST AREA TODAY, ALLOWING  
LOWER SURFACE DEWPOINTS TO CONTINUE FILTERING INTO THE FORECAST  
AREA. AIDED BY BOUNDARY LAYER MIXING, DEWPOINTS IN THE LOWER/MID  
60S, WITH PERHAPS SOME 50S HERE AND THERE ARE EXPECTED THIS  
AFTERNOON. COMBINING THIS WITH MID-LEVEL LAPSE RATES OF LESS THAN 6  
C/KM YIELDS PM FORECAST SOUNDINGS WITH MINIMAL BUOYANCY AND A DECENT  
AMOUNT OF CIN. THAT BEING THE CASE, DEEP CONVECTIVE DEVELOPMENT  
APPEARS UNLIKELY THIS AFTERNOON, AND POPS WILL BE ADVERTISED AT LESS  
THAN 20% IN ALL AREAS. TEMPS WILL ALSO BE A COUPLE OF DEGREES COOLER  
THAN ON FRIDAY, WHICH ALONG WITH THE LOWER DEWPOINTS WILL MAKE FOR A  
COMPARATIVELY PLEASANT DAY AFTER THE MUGGINESS OF THE PAST WEEK. THE  
"NOT-TOO-BAD FOR MID/LATE AUGUST" WEATHER PERSISTS INTO TONIGHT,  
WITH THE DRIER AIR EXPECTED TO ALLOW MIN TEMPS TO SETTLE VERY CLOSE  
TO CLIMO, IF NOT A DEGREE OR TWO LESS IN SOME SPOTS.  
 

 
   
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
 
 
AS OF 200 AM EDT SATURDAY: UPPER LEVEL HEIGHTS WILL BEGIN TO RISE  
AND BROADEN RATHER QUICKLY SUN AS AN H5 TROF LIFTS OVER NEW ENG.  
SUB/TROP RIDGING WILL NUDGE IN FROM THE EAST AS WELL AND MAINTAIN A  
1020 MB HIGH ACROSS THE ERN CONUS. THUS...WITH GOOD INSOL THRU A  
DEEP LAYER...CONVEC AND SHRA WILL BE HARD TO COME BY. MODEL  
SOUNDINGS INDICATE BELOW NORMAL PWATS AND A PRONOUNCED SUBS INVER  
ARND H6. THINK THE BEST SHOT OF THUNDER WILL BE ACROSS THE NC MTNS  
IN RIDGE TOP CONVG WHERE PERHAPS A COUPLE SHORT LIVED STORMS MAY  
DEVELOP DURING THE AFTERNOON. DEEP SFC-BASED MIXING WILL TAP INTO  
DRY AIR ALOFT AND CONTINUE THE RELATIVELY LOW TD/S MAKING FOR A HOT  
BUT NOT UNBEARABLE FEELING DAY FOR MID AUG. A QUIET OVERNIGHT PERIOD  
IS IN STORE AND WEAK LLVL FLOW WILL GRADUALLY SHIFT SE/LY AS THE SFC  
HIGH CENTERS OFF THE MID/ATL COAST.  
 
THIS FLOW WILL ALLOW AN INCREASE IN SFC TDS...BUT NOT ENOUGH TO  
OVERCOME THE DEEP LAYERED NEGATIVE FORCING TO PRODUCE A SIGFNT  
CONVEC THREAT OUTSIDE THE HIGHER TERRAIN. WITH SOME MECH LIFT IN  
PLAY...A FEW STRONGER THERMALLY DRIVEN PULSE STORMS WILL BE  
POSSIBLE ACROSS THE NC MTNS THRU THE AFTERNOON. MOST AREAS OUTSIDE  
THE MTNS WILL SEE LITTLE IF ANY STORMS AS LLVL FORCING WILL REMAIN  
SOUTH OF THE FA AND STRONG RIDGING DOMINATES. THE MODELS AGREE  
FAIRLY WELL WITH KEEPING A STATIONARY FRONT MOISTURE AXIS SITUATED  
ACROSS THE LOW COUNTRY WITH A LITTLE MOVEMENT TO THE NW DURING THE  
DAY LIKELY DUE TO THE SEA BREEZE. THE LATEST NAM IS MORE AGGRESSIVE  
WITH LLVL MOISTURE FLUX THAN THE GFS...BUT AS FAR AS THE IMPACT ON  
CLOUD COVER DURING THE ECLIPSE...IT SHOULDN/T MAKE A NOTICEABLE  
DIFFERENCE. BASICALLY...WILL EXPECT FAIR WEATHER OR SLIGHTLY ENHANCE  
CU TO THE SOUTH COVERING ABOUT 30-40% OF THE SKY DURING THE EARLY  
AFTERNOON AND RATHER GOOD ECLIPSE VIEWING WITH THIS PATTERN. THINGS  
COULD CHANGE DEPENDING ON THE STRENGTH AND ALIGNMENT OF A BUILDING  
ATL SFC RIDGE...BUT FOR NOW THINGS LOOK TO REMAIN ON TRACK SIMILAR  
TO THE PREVIOUS FEW FCSTS. MAX TEMPS MON SHUD STILL REACH THE U80S  
OR L90S NON/MTNS EVEN WITH A 5-7 DEGREE OR SO DROP OFF DURING THE  
ECLIPSE. SFC TD/S WILL REBOUND TO ARND 70 F HOWEVER MAKING FOR  
MUGGY CONDS AND ELEVATED HEAT INDEX VALUES.  
 

 
   
LONG TERM /TUESDAY THROUGH FRIDAY/
 
 
AS OF 245 AM EDT SATURDAY: A PERIOD OF TRANSITION IS IN STORE OVER  
THE MEDIUM RANGE. STRONG ULVL RIDGING WILL CONTINUE TO HOLD A  
STAGNANT WARM AND MOIST AIRMASS OVER THE FA WITH LITTLE FORCING TO  
SPEAK OF OUTSIDE OF LLVL THERMAL LIFT MAINLY ACROSS THE MTNS. LOW  
END POPS HAVE BEEN MAINTAINED WITH THE FAVORED LOCALE BEING THE SW  
NC MTNS IN MODEST UPSLOPE BUT MOIST FLOW. HEIGHTS BEGIN TO FALL WED  
AHEAD OF AN INCOMING H5 WAVE AND AN ATTENDANT SFC FRONT. STRONG  
ENERGY ROUNDING A CLOSED LOW OVER ERN CANADA WILL PUSH THIS FRONT  
INTO AND THRU THE AREA LATE WED WITH PREFRONTAL LIFT BECOMING A  
FOCUSING ZONE FOR STG/SVR STORMS BY MID AFTERNOON. THE FRONT LOOKS  
TO REMAIN PRETTY MUCH INTACT AS IT CROSSES THE HIGH TERRAIN AND IT  
WILL BENEFIT FROM CONTINUED GOM MOISTURE FLUX EARLY ON. THUS...SOME  
ORGANIZATION IS POSSIBLE WITH THIS SYSTEM AS DEEP LAYERED SHEAR  
REACHES 30 KTS OR SO. THE SHEAR MAY NOT BE A HUGE FACTOR HOWEVER AS  
RELATIVELY STRONGER WINDS REMAIN ABOVE H75. BUT NONETHELESS...GOOD  
LLVL FORCING AND AN UNSTABLE AIRMASS WILL BE IN PLAY. A STRONG CP  
HIGH WILL BE FORCED SOUTH ACROSS THE MIDWEST THU AS DEEP H5 RIDGING  
DEVELOPS INTO WRN CANADA. THIS WILL BRING A LOWERING OF TD/S AND  
MAX TEMPS BY A COUPLE CATS OR SO...WHICH SHUD BE REINFORCED FRI AS A  
BROAD SFC HIGH SITUATES ACROSS THE SRN GLAKES REGION. THERE IS STILL  
A SHOT AT SOME AFTERNOON MTN TOP CONVEC...MAINLY SHOWERS...THU AND  
FRI AFTERNOON...BUT THE LATTER HALF OF THE FCST PERIOD WILL SEE  
UNSEASONALLY PLEASANT FEELING WEATHER COMPARED THE RECENT HOT AND  
MUGGY CONDS.  
 

 
   
AVIATION /15Z SATURDAY THROUGH WEDNESDAY/
 
 
AT KCLT AND ELSEWHERE: NO CHANGE TO THE KCLT TAF FOR THE 15Z AMD.  
OTHERWISE, VFR ALONG WITH A CONVECTION-FREE AFTERNOON IS EXPECTED  
THROUGH AT LEAST THIS EVENING. ANOTHER ROUND OF FOG/LOW STRATUS IS  
POSSIBLE IN THE MTN VALLEYS TONIGHT/EARLY, ALTHOUGH CHANCE ARE  
CONSIDERABLY LOWER IN LIGHT OF THE DRIER AIR. THEREFORE, KEPT  
RESTRICTIONS OUT OF KAVL AS WELL AS ALL OTHERS DURING THE OUT  
PERIOD. WINDS WILL GENERALLY FAVOR LIGHT NW THROUGH NE THROUGH THE  
MORNING HOURS, BUT SHOULD BECOME MORE VARIABLE IN DIRECTION THIS  
AFTERNOON.  
 
OUTLOOK: THE INACTIVE PATTERN IS EXPECTED TO CONTINUE INTO EARLY  
NEXT WEEK, ALTHOUGH PATCHY MORNING FOG/STRATUS WILL REMAIN POSSIBLE,  
MAINLY IN THE MOUNTAIN VALLEYS. A MORE TYPICAL LATE SUMMER PATTERN  
RETURNS BY MID-WEEK, WITH ISOLATED/SCATTERED AFTERNOON/EVENING  
STORMS EXPECTED, ALONG WITH BETTER CHANCES FOR PATCHY FOG/LOW  
STRATUS, ESPECIALLY IN THE MTN VALLEYS.  
 
CONFIDENCE TABLE...  
 
15-21Z 21-03Z 03-09Z 09-12Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAVL HIGH 100% HIGH 100% HIGH 100% MED 72%  
KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 94%  
KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAND HIGH 100% HIGH 100% HIGH 100% HIGH 94%  
 
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...SBK  
NEAR TERM...JDL/TDP  
SHORT TERM...SBK  
LONG TERM...SBK  
AVIATION...JDL/TDP  
 
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