630  
FXUS62 KGSP 241835  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
235 PM EDT WED AUG 24 2016  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL PERSIST OVER THE REGION FOR THE NEXT FEW DAYS,  
ALLOWING TEMPERATURES TO CLIMB BACK ABOVE NORMAL. ANOTHER WEAK  
SURFACE FRONT WILL APPROACH THE WESTERN CAROLINAS FROM THE NORTHWEST  
TOWARD THE END OF THE WORK WEEK, WITH HIGH PRESSURE BUILDING BACK TO  
OUR NORTH OVER THE WEEKEND. RAIN CHANCES WILL REMAIN BELOW NORMAL  
THROUGH THE BEGINNING OF NEXT WEEK. ANOTHER FRONT WILL APPROACH THE  
AREA BY THE MIDDLE OF THE NEXT WORK WEEK.  
 

 
   
NEAR TERM /THROUGH THURSDAY/
 
 
AS OF 215 PM: A BROKEN STRATOCU DECK LINGERS OVER THE WRN TWO-THIRDS  
OF THE CWFA, EVIDENTLY BEING MAINTAINED BY WEAK WESTERLY UPGLIDE  
OVER THE HIGH PRESSURE OVER THE EASTERN SEABOARD. THE DECK  
IS BECOMING MORE CELLULAR ON VISIBLE SATELLITE, BUT IN SOME  
PLACES IS BEING REPLACED WITH DIURNAL CUMULUS AS FAST AS IT IS  
DISSOLVING. ISOLATED SHOWERS ARE ALSO DEVELOPING WITHIN THE DECK  
AS DESTABILIZATION OCCURS. MODELS HAVE BACKED OFF THEIR DEPICTIONS  
OF SHRA/TSRA COVERAGE OVER THE HIGH TERRAIN, GIVEN THE DELAYED  
WARMING, BUT THERE STILL IS POTENTIAL FOR WIDELY SCATTERED ACTIVITY  
TO DEVELOP THERE.  
 
THE PATTERN REMAINS LARGELY THE SAME TONIGHT, WITH LOW LEVEL WINDS  
VEERING IN RESPONSE TO A TROUGH MOVING THRU THE NORTHEASTERN CONUS,  
BUT STILL GENERATING WEAK ISENTROPIC LIFT AND BEARING A FAIR AMOUNT  
OF MOISTURE. PATCHY MIDLEVEL CLOUDS THUS ARE EXPECTED TO PERSIST,  
ALBEIT NOT AS UNIFORM AS WHAT WE EXPERIENCED THIS MORNING. GUIDANCE  
CONSENSUS DEVELOPS FOG IN THE MOUNTAIN VALLEYS AND PORTIONS OF  
THE FOOTHILLS BEFORE DAWN, WHICH IN LIGHT OF LIMITED MIXING TODAY  
IS PLAUSIBLE AS LONG AS THE CLOUD DECKS REMAIN BROKEN. MIN TEMPS  
SHOULD BE A TAD ABOVE CLIMO. FOR TOMORROW, I WAS A LITTLE RELUCTANT  
TO REALLY CLEAR SKIES OUT QUICKLY SEEING HOW IT DEVELOPED THIS  
MORNING, SEEING AS THE PATTERN WILL HAVE CHANGED SO LITTLE. ONE  
DIFFERENCE IS THAT WINDS WILL BE MORE DOWNSLOPE, WHICH COULD  
HELP SPEED EROSION. ONCE AGAIN THE MOUNTAINS ARE EXPECTED TO  
DESTABILIZE SUFFICIENTLY TO EXPECT SCATTERED CONVECTION, WITH THE  
PIEDMONT STILL SEEING THE LIMITING EFFECT OF SUBSIDENCE WITHIN  
THE RIDGE AIRMASS. SO POPS ARE LIMITED TO THE HIGH TERRAIN. MAX  
TEMPS ARE EXPECTED TO BE NEAR CLIMO, A BIT WARMER THAN TODAY WITH  
THE EXPECTATION OF LESS CLOUDINESS.  
 

 
   
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/
 
 
AS OF 215 PM EDT WEDNESDAY...THE LATE PART OF THE WEEK STILL LOOKS  
RELATIVELY QUIET AS A MID/UPPER ANTICYCLONE/RIDGE MOVES OVERHEAD ON  
FRIDAY. THIS SHOULD KEEP SOME WARMER AIR ALOFT AND CONVECTIVE  
INHIBITION THAT WILL HELP TO PUT A DAMPER ON THE AMOUNT OF DEEP  
CONVECTION. THUS, HAVE LIMITED THE PRECIP PROBABILITY TO THE LOW END  
OF THE CHANCE RANGE AND ONLY OVER THE HIGHER TERRAIN. TEMPS WILL  
CLIMB BACK ABOVE NORMAL. STARTING ON SATURDAY, UNCERTAINTY RAMPS UP  
WITH REGARD TO THE EFFECT OF THE ANTICYCLONE CENTER MOVING OFF TO  
THE EAST AND THE POSITION OF A WEAK FRONT DRIFTING DOWN FROM THE N.  
THE OPERATIONAL GFS IS MORE RESPONSIVE THAN THE OTHER MODELS,  
PERHAPS BECAUSE OF A STRONGER SE FLOW AT LOW LEVELS WHICH BRINGS IN  
ATLANTIC MOISTURE, WHILE THE OPERATIONAL NAM MIGHT BE TOO DRY  
BECAUSE IT DRIVES THE SURFACE BOUNDARY TO OUR S AND ACTUALLY HAS A  
WEDGE-LIKE CONFIGURATION BY LATE AFTERNOON. THE OFFICIAL FORECAST  
STILL FAVORS THE HIGHER TERRAIN WITH A SLIGHTLY BELOW CLIMO CHANCE  
OF PRECIP, BUT ALLOWS FOR ISOLATED STORMS TO MOVE OUT ACROSS THE  
I-40 CORRIDOR IN THE AFTERNOON AND THE REST OF THE PIEDMONT/UPSTATE  
IN THE EVENING. NOT SURE YET HOW THIS WILL TREND, BUT STILL EXPECT  
PRECIP CHANCES TO BE DIURNAL IN NATURE. TEMPS WILL DEPEND ON THE  
ABILITY OF THE SHALLOW SURFACE BOUNDARY TO SLIP SOUTHWARD. THE  
CHANCE FOR SEVERE STORMS LOOKS LOW.  
 

 
   
LONG TERM /SUNDAY THROUGH WEDNESDAY/
 
 
AS OF 230 PM EDT WEDNESDAY...THE EXTENDED FORECAST BEGINS 12Z SUNDAY  
WITH A LARGE UPPER RIDGE OVER THE SOUTHEAST BEGINNING TO FLATTEN.  
MODEL GUIDANCE DIVERGES ALMOST IMMEDIATELY WITH THE HANDLING OF THIS  
RIDGE AND SUBSEQUENT FEATURES, SO THE FORECAST CONSISTS OF A MULTI-  
MODEL BLEND THAT IS WEIGHTED TOWARDS THE ECMWF, WHICH HAS DISPLAYED  
BETTER RUN-TO-RUN CONSISTENCY THAN THE REST OF THE GLOBAL MODEL  
SUITE OVER THE PAST FEW DAYS. THE UPPER RIDGE DOES MAINTAIN A  
WARMING AND DRYING INFLUENCE OVER THE SOUTHERN APPALACHIANS INTO  
EARLY NEXT WEEK, THOUGH IT BEGINS TO DECAY SOMEWHAT SUNDAY AND  
MONDAY. POPS WERE THEREFORE KEPT BELOW CLIMO THROUGH EARLY NEXT  
WEEK, AND MAXIMUM TEMPERATURES WERE KEPT A FEW DEGREES ABOVE CLIMO.  
A SURFACE FRONTAL BOUNDARY WILL BEGIN TO APPROACH THE AREA NEXT  
TUESDAY, THOUGH ITS TIMING AND THE AMOUNT OF MOISTURE IT HAS TO WORK  
WITH ARE DEPENDENT ON THE TRACK AND INTENSITY OF A POTENTIAL  
TROPICAL SYSTEM THAT IS BEING INVESTIGATED BY THE NATIONAL HURRICANE  
CENTER. MOST MODELS NOW SHOW SOME DEVELOPMENT OF THE SYSTEM, AND  
THOUGH THE TRACKS OF THE SYSTEM IN THE MAJOR MODELS ARE CURRENTLY  
QUITE DIFFERENT, IT APPEARS THAT NO DIRECT IMPACT FROM IT WILL OCCUR  
IN OUR AREA THROUGH THE NEXT SEVEN DAYS. THE ECMWF ALLOWS FOR MORE  
MOISTURE RETURN INTO THE SOUTHEAST, SO POPS WERE ELEVATED TO  
NEAR/JUST ABOVE CLIMO BY THE MIDDLE OF NEXT WEEK. OVERALL, LITTLE  
CHANGE WAS MADE TO THE PREVIOUS MEDIUM RANGE FORECAST, ESPECIALLY  
CONSIDERING THE LARGE AMOUNT OF UNCERTAINTY IN GLOBAL MODEL  
SOLUTIONS AT THE CURRENT TIME.  
 

 
   
AVIATION /19Z WEDNESDAY THROUGH MONDAY/
 
 
AT KCLT AND ELSEWHERE: OFFSHORE ATLANTIC HIGH PRESSURE WILL  
GENERALLY MAINTAIN SOUTHERLY SURFACE FLOW OVER THE AREA THRU  
THURSDAY. HOWEVER, MOIST WEST-SOUTHWEST FLOW ATOP THIS AIRMASS  
HAS BROUGHT A PERSISTENT AREA OF STRATOCUMULUS TO THE SOUTHERN  
APPALACHIANS AND VICINITY. THESE CLOUDS ARE SHOWING SIGNS OF  
BREAKING UP AND LIFTING AT 18Z, BUT WILL PERSIST IN SOME PLACES  
THRU EVENING. SUFFICIENT DESTABILIZATION IS EXPECTED OVER THE  
MTNS TO PROMPT VCTS INCLUSION AT KAVL. WINDS ALOFT WILL VEER AND  
BRING IN ADDITIONAL MOISTURE OVERNIGHT. LOW VFR CIGS ARE LIKELY  
TO COME AND GO THROUGHOUT THE PERIOD. MODELS DEPICT ONLY A SMALL  
AMOUNT OF RESTRICTIVE CLOUDS OVERNIGHT, GENERALLY FAVORING THE  
PRODUCTION OF FOG INSTEAD. WITH SO MUCH HIGHER CLOUD COVER PRESENT,  
AND UNCERTAINTY ABOUT HOW MUCH MIXING/DRYING WILL OCCUR IN THE  
LOW LEVELS THIS AFTN, FOG MENTION IS INCLUDED ONLY IN TEMPO AT  
KAVL/KHKY; AT KAND NEARBY SOAKING RAINS EARLIER TODAY WILL PLAY  
A FACTOR.  
 
OUTLOOK: A DEEP RIDGE WILL REMAIN IN PLACE OVER THE SOUTHEAST THRU  
THE WEEKEND, KEEPING AFTERNOON SHRA/TSRA CHANCES BELOW NORMAL EACH  
DAY, AND GENERALLY CONFINED TO THE MOUNTAINS. HOWEVER, SFC MOISTURE  
WILL GRADUALLY RETURN, AND MORNING VSBY RESTRICTIONS WILL BECOME  
INCREASINGLY LIKELY DURING THIS TIME.  
 
CONFIDENCE TABLE...  
 
18-24Z 00-06Z 06-12Z 12-18Z  
KCLT HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KGSP HIGH 100% HIGH 97% HIGH 80% HIGH 91%  
KAVL HIGH 98% HIGH 94% HIGH 84% HIGH 84%  
KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 91%  
KGMU HIGH 100% HIGH 97% MED 75% HIGH 91%  
KAND HIGH 100% HIGH 100% HIGH 86% HIGH 88%  
 
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...LEV  
NEAR TERM...WIMBERLEY  
SHORT TERM...PM  
LONG TERM...LEV  
AVIATION...WIMBERLEY  
 
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