001  
FXUS62 KGSP 250230  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
1030 PM EDT SAT SEP 24 2016  
   
SYNOPSIS
 
 
A BROAD UPPER RIDGE AND SURFACE HIGH PRESSURE WILL REMAIN IN PLACE  
OVER THE SOUTHEAST THROUGH TONIGHT, THEN BREAK DOWN SUNDAY AS AN  
UPPER TROUGH APPROACHES FROM THE MISSISSIPPI VALLEY. A SLIGHTLY  
COOLER AND MOIST AIRMASS WILL BEGIN SUNDAY AS A FRONTAL BOUNDARY  
SETTLES INTO THE AREA FROM THE NORTH. UNSETTLED WEATHER IS LIKELY TO  
LINGER THROUGH THE FIRST HALF OF NEXT WEEK BEFORE DRIER AND COOLER  
AIR ENTERS BEHIND THE PASSING COLD FRONT BY THE MIDDLE OF NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH SUNDAY/
 
 
AS OF 1030 PM: RECENT SATELLITE IMAGES INDICATED A FEW PATCHES OF  
CLOUDS ACROSS THE NC FOOTHILLS AND MTNS. I WILL UPDATE THE FORECAST  
TO ADJUST SKY COVER TO SATELLITE DATA. OTHERWISE, THE CURRENT  
FORECAST APPEARS TO BE IN GOOD SHAPE.  
 
AS OF 745 PM: LIGHT WINDS WITH THIN HIGH CLOUDS EXPECTED ACROSS THE  
WESTERN CAROLINAS THROUGH MUCH OF TONIGHT. DURING THE PRE DAWN  
HOURS, NAM INDICATES THAT THE NOSE OF SFC RIDGING AND BACKDOOR COLD  
FRONT WILL PUSH SW ACROSS VA, REACHING THE I-40 CORRIDOR BY SUNRISE.  
NEAR AND BEHIND THE LEADING EDGE OF THE COLD FRONT SHOULD BE THE  
FAVORED AREA FOR STRATUS TO FORM. OTHERWISE, THE CWA SHOULD SEE A WIND  
SHIFT FROM THE NE WITHIN ONE TO TWO HOURS FOLLOWING SUNRISE. DURING  
LATE SUNDAY AFTERNOON, THE BACKDOOR COLD FRONT IS FORECAST TO PUSH  
ACROSS THE UPSTATE OF SC INTO THE UPPER SAVANNAH RIVER VALLEY. THE  
TIMING OF THE FRONT SHOULD RESULT IN THE OVERLAP OF WEAKEST CIN AND  
HIGHEST CAPE. I WILL INCREASE THE MENTION OF TSRA ALONG AND AHEAD OF  
THE FRONT.  
 
AS OF 510 PM: KGSP RADAR INDICATED A FEW SHOWERS ACROSS THE WESTERN  
NC MTN COUNTIES. I WILL UPDATE THE FORECAST TO INCREASE POPS TO SCHC  
UNDER THE SHOWERS THROUGH 23Z. OTHERWISE, I WILL KEEP TEMPS NEARLY  
STEADY OVER THE NEXT HOUR, THEN DIURNAL COOLING THROUGH THE EVENING.  
KAVL TIED TODAYS HIGH TEMPERATURE OF 89 SET IN 1895.  
 
PREVIOUS DISCUSSION...  
AREAS OF FEW-SCT CU AND MAYBE A SMALL SW NC RIDGETOP SHOWER WILL  
DISSIPATE WITH LOSS OF HTG EARLY THIS EVENING. STILL EXPECTING A  
BACK DOOR COLD FRONT TO APPROACH FROM THE NORTH TONIGHT WITH AN  
ACCOMPANYING WIND SHIFT BACK TO NE AND AN ASSOCIATED STRATOCU FIELD  
ACROSS WESTERN NC DURING THE LATE NIGHT HOURS. THE SOUTHWARD PUSH  
OF SAID BOUNDARY IS EXPECTED TO SLOW ON SUNDAY, AS IT BECOMES  
PARALLEL TO THE UPPER FLOW. THIS MAY SERVE AS A FOCUS FOR SCATTERED  
DEEPER CONVECTION DURING THE AFTERNOON ALONG WITH SCATTERED ACTIVITY  
IN THE FAVORED TERRAIN-AIDED LOCALES. WITH THE PUSH OF LOWER  
THICKNESS VALUES INTO THE NORTHERN CWFA, AND THE POTENTIAL FOR  
CLOUDY SKIES TO START OFF THE DAY ON SUNDAY, MAXIMUM TEMPERATURES  
ARE SLATED TO BE 10-12 DEG F COOLER THAN TODAY ALONG I-40, BUT WILL  
BE CLOSE TO PERSISTENCE ON THE WARM SIDE OF THE FRONT, ACRS THE FAR  
SW CWFA.  
 

 
   
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
 
 
AS OF 235 PM EDT SATURDAY: BACK DOOR COLD FRONT REMAINS STALLED  
ACROSS THE AREA SUNDAY NIGHT WITH HIGH PRESSURE WEAKLY RIDGED INTO  
THE AREA FROM THE NE. WITH A MOIST LOW LEVEL SOUTHERLY FLOW IN  
PLACE, EXPECT SCATTERED SHOWERS TO REMAIN OVER THE AREA THROUGH THE  
NIGHT. ANY STORMS SHOULD BE PUSHED SOUTHEAST TOWARD THE FRONTAL  
BOUNDARY. LOWS WILL BE AROUND 10 DEGREES ABOVE NORMAL.  
 
THE FRONT WILL WASH OUT ON MONDAY AS A COLD FRONT MOVES TO THE SPINE  
OF THE APPALACHIANS AND INTO THE AREA MONDAY NIGHT. THE MOIST LOW  
LEVEL SOUTHERLY FLOW CONTINUES THROUGH BOTH PERIODS. EXPECT AT LEAST  
GOOD COVERAGE OF SHOWERS ACROSS THE AREA WITH SCATTERED  
THUNDERSTORMS AS MODERATE INSTABILITY DEVELOPS. EVEN WITH THE FRONT,  
SHEAR REMAINS LIGHT, SO SEVERE CHANCES ARE MINIMAL. HOWEVER, THERE  
SHOULD BE SOME BENEFICIAL RAINFALL WITH THE CONVECTION AS QPF  
FORECASTS ARE UP TO HALF AN INCH ACROSS THE MOUNTAINS AND FOOTHILLS.  
HIGHS MONDAY WILL BE COOLER "ONLY" UP TO 5 DEGREES ABOVE NORMAL.  
LOWS MONDAY NIGHT WILL BE 5 TO 10 DEGREES ABOVE NORMAL.  
 
THE GUIDANCE SHOWS A LITTLE TIMING DIFFERENCE ON THE SPEED OF THE  
COLD FRONT MOVING THROUGH THE AREA ON TUESDAY. BEST CHANCE OF  
PRECIPITATION WILL BE OUTSIDE OF THE MOUNTAINS WITH ANY SOLUTION.  
THAT SAID, SCATTERED CONVECTION IS EXPECTED DURING THE MORNING EVEN  
WHERE CHANCES ARE LOWER. INSTABILITY SHOULD REMAIN WEAK, BUT HIGH  
ENOUGH FOR SCATTERED THUNDERSTORMS, ESPECIALLY OUTSIDE OF THE  
MOUNTAINS. HIGHS WILL BE NEAR NORMAL MOUNTAINS AND A COUPLE OF  
DEGREES ABOVE ELSEWHERE.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
 
 
AS OF 150 PM EDT SATURDAY: WE BEGIN THE MEDIUM RANGE/EXTENDED WITH A  
CHANGE IN AIRMASS TUESDAY NIGHT AS THE COLD FRONT MOVES EAST AND  
AWAY FROM THE INTERSTATE 85 CORRIDOR TOWARD THE COAST. THE FORECAST  
DEEP CLOSED UPPER LOW WILL BE CENTERED OVER THE GREAT LAKES TUESDAY  
NIGHT. THE ECMWF HAS THIS LOW CENTERED OVER THE WESTERN CAROLINAS  
THURSDAY NIGHT. THE GFS ON THE OTHER HAND HAS THIS LOW OPENING UP  
WITH THE WESTERLY FLOW WEDNESDAY NIGHT AND MOVING THE TROUGH EAST  
AND OFF THE EAST COAST BY THURSDAY NIGHT. WE WILL BE KEEPING THE  
MEDIUM RANGE FORECAST DRY AFTER THE FEW DEPARTING SHOWERS EARLY  
WEDNESDAY. AT THIS TIME DO NOT BELIEVE THE CLOSED LOW WILL WOBBLE  
THIS FAR SOUTH ALONG THERE IS A POSSIBILITY THAT THE CLOSED LOW WILL  
BECOME DETACHED FROM THE WESTERLIES AND WOBBLE AROUND FOR A FEW  
DAYS.  
 
TEMPERATURES WILL BE NEAR NORMAL WEDNESDAY THEN ABOUT A CATEGORY  
BELOW NORMAL THURSDAY THROUGH SATURDAY.  
 

 
   
AVIATION /03Z SUNDAY THROUGH THURSDAY/
 
 
AT KCLT AND ELSEWHERE: LIGHT WINDS WITH THIN HIGH CLOUDS EXPECTED  
ACROSS THE WESTERN CAROLINAS THROUGH MUCH OF TONIGHT. DURING THE PRE  
DAWN HOURS, NAM INDICATES THAT THE NOSE OF SFC RIDGING AND BACKDOOR  
COLD FRONT WILL PUSH SW ACROSS VA, REACHING THE I-40 CORRIDOR BY  
SUNRISE. NEAR AND BEHIND THE LEADING EDGE OF THE COLD FRONT SHOULD  
BE THE FAVORED AREA FOR STRATUS TO FORM. I WILL INDICATE SCT IFR  
LEVEL STRATUS AT KHKY BY THE MID MORNING HOURS. OTHERWISE, TERMINALS  
SHOULD SEE A WIND SHIFT FROM THE NE WITHIN ONE TO TWO HOURS  
FOLLOWING SUNRISE. DURING LATE SUNDAY AFTERNOON, THE BACKDOOR COLD  
FRONT IS FORECAST TO PUSH ACROSS THE UPSTATE OF SC INTO THE UPPER  
SAVANNAH RIVER VALLEY. THE TIMING OF THE FRONT SHOULD RESULT IN THE  
OVERLAP OF WEAKEST CIN AND HIGHEST CAPE. I WILL ADD A PROB30 FOR  
KGMU, KAND, AND KAVL FOR -TSRA BETWEEN 21Z TO 24Z.  
 
OUTLOOK: A BACK DOOR COLD FRONT WILL PUSH INTO THE REGION ON SUNDAY,  
BRINGING INCREASED MOISTURE FOR EARLY NEXT WEEK. ANOTHER COLD FRONT  
WILL PUSH IN FROM THE WEST ON TUESDAY, BRINGING THE BEST CHANCE FOR  
SHOWERS AND POSSIBLY SOME TSTMS. THEN DRY HIGH PRESSURE RETURNS  
MIDWEEK.  
 
CONFIDENCE TABLE...  
 
02-08Z 08-14Z 14-20Z 20-00Z  
KCLT HIGH 100% HIGH 100% HIGH 89% HIGH 91%  
KGSP HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAVL HIGH 100% HIGH 91% HIGH 100% HIGH 100%  
KHKY HIGH 100% HIGH 98% MED 69% HIGH 100%  
KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 100%  
KAND HIGH 100% HIGH 87% 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...NED  
SHORT TERM...RWH  
LONG TERM...DEO  
AVIATION...NED  
 
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