280  
FXUS62 KGSP 231515  
AFDGSP  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC  
1115 AM EDT FRI JUN 23 2017  
   
SYNOPSIS
 
 
SHOWER AND THUNDERSTORM COVERAGE ASSOCIATED WITH THE REMNANTS OF  
CINDY AND AN APPROACHING COLD FRONT WILL INCREASE FROM THE WEST  
TONIGHT INTO EARLY SATURDAY MORNING. LIGHT SHOWERS WILL LINGER  
SATURDAY MORNING AS THE FRONT SLOWLY CROSSES THE AREA, AND  
THUNDERSTORMS MAY REDEVELOP JUST AHEAD OF THE COLD FRONT OVER THE  
PIEDMONT. UNSEASONABLY COOL AND DRY CONDITIONS WILL SPREAD OVER THE  
FORECAST AREA IN THE WAKE OF THE FRONT AND PERSIST THROUGH THE  
MIDDLE OF NEXT WEEK.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 1105 AM EDT: MOSTLY GOOD INSOLATION AND A WARM START FOR MUCH  
OF THE AREA WILL REQUIRE ABOUT A ONE DEGREE INCREASE IN MAX TEMPS  
THIS AFTERNOON, BUT DEVELOPING CLOUDS IN HEATING WITH GOOD BOUNDARY  
LAYER MOISTURE COULD INHIBIT INSOLATION AT TIMES.  
 
OTHERWISE, THE REMNANT CIRCULATION OF CINDY WAS MOVING INTO FAR  
WESTERN TN LATE THIS MORNING, WITH ASSOCIATED TROPICAL MOISTURE  
FILLING IN EAST OF THE MS RIVER AND ACROSS CENTRAL AND WESTERN TN.  
THE CINDY REMNANTS WILL CONTINUE TO GET SLOWLY ABSORBED BY THE BROAD  
LONGWAVE TROUGH IN PLACE OVER THE NORTHERN TIER OF THE COUNTRY. THE  
UPPER RIDGE OVER THE SOUTHEAST WILL SLOWLY FLATTEN AND BE PUSHED  
SOUTH AS THE PHASED TROUGH PUSHES INTO THE APPALACHIANS TONIGHT. WE  
COULD SEE SOME DIURNALLY-DRIVEN SCATTERED CONVECTION ACROSS THE  
MOUNTAINS, BUT THEN A NON-DIURNAL RAMPUP OF CONVECTION SHOULD START  
THIS EVENING. THE INCREASING SURFACE PRESSURE GRADIENT AS THE  
REMNANT CINDY SURFACE CIRCULATION APPROACHES SHOULD LEAD TO BREEZY  
SOUTH/SOUTHEAST WINDS WHICH MAY PROVIDE AT LEAST SOME RELIEF FROM  
THE HUMIDITY.  
 
AS WE MOVE THROUGH THIS EVENING AND THE FRONT APPROACHES, CONVECTION  
SHOULD BEGIN WITH SOME UPSLOPE SHOWERS IN THE SOUTHWEST MOUNTAINS,  
WITH A POTENTIAL CONVECTIVE LINE MOVING INTO WESTERN ZONES SOMETIME  
AFTER 00Z. SURFACE-BASED INSTABILITY WILL BE LIMITED, BUT SHOULD  
STILL SEE CAPES SLOWLY INCREASE TO BETWEEN 500-750ISH J/KG AHEAD OF  
THE FRONT. DEEP-LAYER SHEAR WILL MOVE IN AS WELL WITH A 50+KT 850MB  
LLJ AHEAD OF CINDY'S ABSORBED REMNANTS, WITH RESULTING 0-6KM BULK  
SHEAR GENERALLY 30-40KT, BUT COULD CREEP UP TOWARD 50KT. SO WITH  
THIS, DESPITE THE OVERALL LACK OF WIDESPREAD INSTABILITY, CANNOT  
RULE OUT ISOLATED SEVERE CONVECTION, AND AS WITH ANY TROPICAL  
REMNANTS, MINI SUPERCELLS AND PERHAPS A BRIEF TORNADO CANNOT BE  
RULED OUT. SPC'S MARGINAL RISK LOOKS TO COVER THIS WELL, BUT THE  
PROBLEM IS THAT ANYTHING THAT DOES OCCUR WOULD BE NOCTURNAL.  
 
OTHER CONCERN IS RAINFALL, BUT IT REALLY LOOKS LIKE THE MOUNTAINS  
WILL BREAK UP QUITE A BIT OF THE WIDESPREAD HEAVY RAIN. DAY 1 QPF  
ISN'T ALL THAT IMPRESSIVE, WITH AROUND 1.5" IN EXTREME WESTERN  
GRAHAM COUNTY (HIGHEST IN THE CWA)...AND THOUGH 1HR FFG IS 1-3",  
THAT 1.5" IN 24H WAS ENOUGH TO WARRANT A SLIGHT RISK OF EXCESSIVE  
RAIN. FOR NOW, IT JUST DOESN'T SEEM LIKE ENOUGH CONCERN OF FOR A  
FLASH FLOOD WATCH. NO DOUBT TRAINING CONVECTIVE CELLS MAY LEAD TO AN  
ISOLATED THREAT ESPECIALLY IN THE MOUNTAINS, AND WITH SOILS FAIRLY  
WET (ESPECIALLY AFTER THIS MORNING'S RAIN) IT PROBABLY WOULDN'T TAKE  
MUCH. BUT JUST NOT ENOUGH CONFIDENCE FOR A WATCH AT THIS TIME.  
 

 
   
SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/
 
 
AS OF 305 AM EDT FRIDAY: THE SHORT-TERM FCST PICKS UP AT 12Z ON  
SATURDAY WITH LONGWAVE UPPER TROFING DIGGING DOWN ACROSS THE GREAT  
LAKES AND STEEP UPPER RIDGING OVER THE WEST AND EAST COASTS. THE  
UPPER LVL PATTERN IS NOT EXPECTED TO CHANGE MUCH THRU THE PERIOD  
WITH THE TROF AXIS REMAINING JUST TO OUR NW AND THE RIDGE AMPLIFYING  
TO OUR WEST. AT THE SFC, A ROBUST-LOOKING COLD FRONT WILL BE MOVING  
THRU THE CWFA BY EARLY SAT, WITH WIDESPREAD SHOWERS AND THUNDERSTORMS  
LIKELY AS IT DOES. THE MODELS ARE HESITANT TO MOVE THE FRONT SOUTH  
OF THE CWFA ON SATURDAY AND KEEP THE BNDY JUST TO OUR SOUTHEAST THRU  
SUNDAY. BY THE END OF THE PERIOD EARLY MONDAY, STRENGTHENING CANADIAN  
HIGH PRESSURE TO OUR NW FINALLY PUSHES THE BNDY OFFSHORE. PRECIPITATION  
CHANCES WILL STEADILY DIMINISH SAT NIGHT THRU EARLY SUN WITH THE REST  
OF SUNDAY EXPECTED TO BE DRY AND A BIT COOLER.  
 

 
   
LONG TERM /MONDAY THROUGH THURSDAY/
 
 
AS OF 255 AM EDT FRIDAY: THE EXTENDED FCST PICKS UP AT 12Z ON MONDAY  
WITH A BROAD LONGWAVE UPPER TROUGH CENTERED OVER THE GREAT LAKES TO  
OUR NW. A REINFORCING UPPER SHORTWAVE DIGS SOUTHWARD ON THE BACKSIDE  
OF THE TROF AND MOVES OVER THE FCST AREA ON TUESDAY. AS THE SHORTWAVE  
LIFTS NE, HEIGHTS BEGIN TO REBOUND AS UPPER RIDGING BEGINS TO BUILD  
TO OUR SOUTH. AT THE SFC, COOLER AND DRIER SHOULD BE IN PLACE OVER  
THE CWFA BY EARLY MONDAY WITH BROAD HIGH PRESSURE CENTERED TO OUR NW  
AND A FRONTAL BNDY TO OUR SE. OVER THE NEXT FEW DAYS, THE HIGH WILL  
SLIDE SE AND OVER THE FCST AND EVENTUALLY MOVE OFF THE ATLANTIC COAST  
BY THE END OF THE PERIOD LATE THURSDAY/EARLY FRIDAY. AS FOR THE SENSIBLE  
WX, THE PERIOD SHOULD BE MOSTLY DRY WITH ONLY SOME SLIGHT CHANCE POPS  
TOWARDS THE END OF THE PERIOD WHEN WE GET BACK UNDER MORE MOIST SOUTHERLY  
FLOW. TEMPS AND DEWPTS WILL REMAIN BELOW NORMAL FOR LATE JUNE WITH VALUES  
WARMING BACK TO NEAR NORMAL BY DAY 7.  
 

 
   
AVIATION /15Z FRIDAY THROUGH TUESDAY/
 
 
AT KCLT AND ELSEWHERE: LINGERING LATE MORNING MVFR CIGS WILL  
CONTINUE TO SCATTER THROUGH NOON, WITH VFR CONDITIONS THROUGH THE  
DAY AND BREEZY S/SW WINDS AS THE PRESSURE GRADIENT INCREASES AHEAD  
OF THE APPROACHING FRONT. FRONT PUSHES IN THIS EVENING AND TONIGHT,  
WITH CONVECTION DEVELOPING ACROSS THE MOUNTAINS AHEAD OF IT. SOME  
QUESTION AS TO THE AMOUNT OF INSTABILITY THAT WILL LEAD TO TSRA, SO  
HAVE INCLUDED SOME PROB30S AFTER ABOUT 06Z FOR THE UPSTATE TAFS AND  
KAVL, BUT ONLY VCSH OR PROB30 -SHRA FOR KHKY/KCLT. WILL LIKELY SEE A  
WIND SHIFT BY THE END OF THE PERIOD FOR KAVL, WITH PLENTIFUL  
MOISTURE LEADING TO ANOTHER ROUND OF MVFR TO POSSIBLE IFR  
RESTRICTIONS.  
 
OUTLOOK: ABUNDANT MOISTURE WILL CONTINUE INTO SATURDAY WITH  
ASSOCIATED RESTRICTIONS AND POSSIBLE CONVECTION. THE FRONT WILL PUSH  
THROUGH ON SUNDAY TO USHER IN A PERIOD OF DRIER WEATHER THROUGH THE  
MIDDLE OF NEXT WEEK.  
 
CONFIDENCE TABLE...  
 
15-21Z 21-03Z 03-09Z 09-12Z  
KCLT HIGH 90% HIGH 100% HIGH 100% MED 60%  
KGSP HIGH 98% HIGH 100% HIGH 100% HIGH 89%  
KAVL HIGH 100% HIGH 100% HIGH 100% HIGH 84%  
KHKY HIGH 100% HIGH 100% HIGH 100% HIGH 98%  
KGMU HIGH 100% HIGH 100% HIGH 100% HIGH 94%  
KAND HIGH 100% HIGH 100% HIGH 100% MED 75%  
 
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...JPT  
NEAR TERM...HG/TDP  
SHORT TERM...JPT  
LONG TERM...JPT  
AVIATION...HG/TDP  
 
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