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Local forecast by
"City, St"
  
000
FXUS62 KGSP 230222
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
1022 PM EDT TUE JUL 22 2014

.SYNOPSIS...
EXPECT A BRIEF RETURN TO MORE TYPICAL SUMMER WEATHER ON WEDNESDAY
BEFORE A FRONT APPROACHES AND MOVES ACROSS THE REGION ON THURSDAY. 
THE PASSAGE OF THE FRONT WILL NOT BRING COOLER AIR...BUT IT SHOULD 
BRING DRIER AIR FOR FRIDAY AND INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 1020 PM...ONLY A FEW SHRA REMAIN ACROSS VARIED PARTS OF THE 
CWFA THIS EVENING. ISOLATED SHRA MAY CONTINUE UNTIL SHORTLY AFTER 
MIDNIGHT BUT SHUD END SHORTLY THEREAFTER. CURRENTLY MUCH LESS 
CLOUDINESS THAN THE MDLS WERE SUGGESTING. HAVE BACKED OFF ON CLOUDS 
THIS EVENING...BUT ALLOW SOME CLOUDS TO DEVELOP AFTER MIDNIGHT. LOWS 
LOOK ON TRACK.

AS OF 740 PM...CONVECTIVE COVERAGE BEGINNING TO WANE WITH THE LOSS 
OF HEATING. COVERAGE WILL CONTINUE TO DIMINISH THRU THE EVENING WITH 
MOST CELLS GONE BY MIDNIGHT. HAVE UPDATED POP FOR THESE TRENDS. HAVE 
BACKED OFF ON CLOUDS EARLY AS WELL GIVEN SAT PIX...BUT STILL EXPECT 
LOW CLOUDS TO RETURN OVERNIGHT. OTHERWISE...GOING FORECAST ON TRACK 
WITH UPDATES MAINLY FOR CURRENT CONDITIONS.

AS OF 420 PM...CONVECTION DEVELOPING ALONG AND SOUTH OF THE I-85 
CORRIDOR AND SLOWLY MOVING NE. EXPECT THESE TRENDS TO CONTINUE INTO 
THE EVENING WITH GREATEST COVERAGE OUTSIDE OF THE MTNS EARLY...THEN 
ACROSS THE MTNS NEAR SUNSET. CONVECTION SHUD THEN SLOWLY TAPER OFF 
WITH ONLY ISOLATED COVERAGE EXPECTED AFTER MIDNIGHT. HAVE UPDATED 
POP...MAINLY EARLY...FOR THESE TRENDS. REST OF THE FCST LOOKS TO BE 
IN GOOD SHAPE WITH ONLY UPDATES FOR CURRENT CONDITIONS NEEDED.

AT 230 PM EDT TUESDAY... FOR THE REMAINDER OF THE AFTERNOON AND 
EVENING... SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL PERSIST 
IN A MOIST BUT ONLY MODESTLY UNSTABLE AIR MASS. NO SIGNIFICANT 
SURFACE FEATURES EXIST IN THE CWA TO PROVIDE AN OBVIOUS FOCUS FOR 
CONVECTIVE DEVELOPMENT. EXPECT SHOWERS TO DRIFT SLOWLY TO THE 
NORTHWEST WITH PERHAPS A SLIGHT PREFERENCE FOR ENHANCEMENT AND BEST 
COVERAGE THIS EVENING IN AREAS WITH UPSLOPE FLOW. WINDS ALOFT 
THROUGH THE EVENING WILL REMAIN QUITE LIGHT IN THE COL REGION OF THE 
MID AND UPPER TROPOSPHERIC HEIGHT FIELD... SO SLOW MOVEMENT OF 
CONVECTIVE CELLS IS LIKELY. OVERNIGHT FOG IS POSSIBLE... BUT MODELS 
AT THIS TIME ARE NOT DEFINITIVE IN INDICATING WIDESPREAD LOW 
VISIBILITY CONDITIONS. NONETHELESS... THE POTENTIAL BEARS WATCHING 
OVERNIGHT. THE PRIME AREA FOR SIGNIFICANT FOG WILL BE IN THE 
MOUNTAIN VALLEYS AND ACROSS THE NORTHERN FOOTHILLS INTO THE 
NORTHWEST PIEDMONT OF NC.

UPPER LEVEL PATTERN ACROSS THE AREA WILL UNDERGO A TRANSITION 
TONIGHT AND WEDNESDAY. THE CUTOFF LOW OVER GULF COAST STATES WILL 
CONTINUE A SLOW DRIFT TO THE WEST AND HEIGHTS WILL FALL TO OUR NORTH 
IN ADVANCE OF SIGNIFICANT TROUGH DIGGING INTO THE EAST. AS TROUGH 
HEADS ACROSS THE GREAT LAKES TOWARD THE ATLANTIC COAST... THE 
SURFACE RIDGE THAT HAS EXTENDED FROM THE MID-ATLANTIC INTO THE 
CAROLINAS FOR A COUPLE OF DAYS WILL DISAPPEAR. IN ITS PLACE WE ARE 
LIKELY TO HAVE A LEE TROUGH RETURN TO THE PIEDMONT PORTION OF THE 
CWA BY WEDNESDAY AFTERNOON. THE FALLING HEIGHTS AND APPROACHING 
DIGGING TROUGH WEDNESDAY AFTERNOON WILL BE ACCOMPANIED BY A WESTERLY 
WIND FLOW ALOFT AND SOUTH TO SOUTHWEST WIND IN THE BOUNDARY LAYER. 
THE RESULT WILL BE A RETURN TO A MORE DIURNAL PATTERN OF CONVECTION 
WITH THE HIGHEST POPS OVER AND NEAR THE HIGHER TERRAIN. WITHOUT A 
MAJOR CHANGE IN AIR MASS... SIGNIFICANT TEMPERATURE CHANGES WILL NOT 
OCCUR. TUESDAY MORNING LOWS ARE EXPECTED TO BE NEAR 70 WITH 60S IN 
THE MOUNTAIN VALLEYS. WEDNESDAY AFTERNOON TEMPERATURES WILL BE 
BETWEEN 85 AND 90 EXCEPT IN THE LOWER AND MIDDLE 80S IN THE MOUNTAIN 
VALLEYS.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
AS OF 200 PM EDT TUESDAY...ALL NUMERICAL GUIDANCE IS FORECASTING A 
STRONG SHORT WAVE TO MOVE THROUGH THE GREAT LAKES WED NIGHT INTO THU 
WHICH WILL DRIVE A SURFACE COLD FRONT SOUTHEASTWARD INTO THE 
SOUTHEAST STATES. THE NAM AND GFS HAVE SETTLED ON SIMILAR TIMING 
IN REGARD TO THE FRONT WITH BOTH MODELS BRINGING IT TO JUST NW OF 
THE NC MOUNTAINS BY 12Z THU...AND THEN BRINGING IT ACROSS THE 
MOUNTAINS INTO THE LOWER PIEMDONT BY THURSDAY EVENING. THE FRONT IS 
THEN FORECAST TO CLEAR THE AREA BY MIDNIGHT. A DRYER AND MORE STABLE 
AIR MASS IS EXPECTED TO OVERSPREAD THE AREA ON FRIDAY AS HIGH 
PRESSURE RIDGES SOUTHEASTWARD FROM THE OHIO VALLEY. 

IN REGARD TO SENSIBLE WEATHER...SOME LINGERING SHOWERS AND STORMS 
MAY BE OVER THE AREA WED EVENING...BUT THEY SHOULD DISSIPATE WITH 
LOSS OF HEATING WED NIGHT. HOWEVER...WILL NEED TO RAMP POPS UPWARD 
LATE THURSDAY NIGHT AS SOME PREFRONTAL SHOWERS MAY REACH THE 
MOUNTAINS BY SUNRISE THURSDAY. WILL CONTINUE TO ADVERTISE LIKELY 
POPS IN PORTIONS OF THE MOUNTAINS AND ALSO IN NC PIEDMONT ON THU 
AFTERNOON...BUT CONVECTION SHOULD BE SCATTERED ELSEWHERE AS WINDS IN 
PROFILES ARE DECIDELY DOWNSLOPE IN NATURE. THERE SHOULD BE PLENTY OF 
INSTABILITY THU AFTERNOON WITH CAPES POOLING TO 1500-2000J OVER THE 
PIEMDONT. HENCE...A FEW SEVERE STORMS ARE POSSIBLE. WILL FORECAST 
DECREASING POPS THU NIGHT AND THEN A DRY DAY ON FRI. MAX TEMPS WILL 
BE BELOW CLIMO BOTH THU AND FRI IN THE MOUNTAINS...BUT NEAR CLIMO 
OUTSIDE THE MOUNTAINS ON THU AND THEN ABOUT A CATEGORY BELOW CLIMO 
ON FRIDAY.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
AS OF 215 PM TUESDAY...THE MEDIUM RANGE GUIDANCE SUGGESTS THAT THE 
EASTERN U.S. TROUGH WILL FLATTEN AS HEIGHTS RISE IN RESPONSE TO 
ANOTHER STRONG UPPER WAVE DIGGING INTO THE NORTHERN PLAINS OVER THE 
WEEKEND. THIS WAVE IS FORECAST TO SWING ACROSS THE GREAT LAKES AND 
RE-ESTABLISH THE EASTERN U.S TROUGH BY MONDAY. 

LOOKS LIKE WE SHOULD BE ABLE TO SQUEEZE OUT ONE MORE NICE DAY ON 
SATURDAY BEHIND THE THURSDAY FRONTAL PASSAGE AS HIGH PRESSURE 
REMAINS WEEKLY RIDGED OVER THE AREA AND MOISTURE LEVELS REMAIN 
RELATIVELY LOW. HOWEVER...IT LOOKS LIKE THE FIRST PART OF NEXT
WEEK WILL TURN STORMY. ALL THE MEDIUM RANGE MODELS HINT AT A 
POSSIBLE MCS MAKING A RUN AT THE SOUTHERN APPALACHIANS ON SUNDAY. IT 
IS DIFFICULT TO SAY WHETHER ANY OF THE PARENT STORMS WILL MAKE IT 
ACROSS THE MOUNTAINS...BUT THE OUTFLOW MAY TRIGGER ADDITIONAL STORMS 
ACROSS THE PIEDMONT SUNDAY AFTERNOON AND NIGHT. ALSO..AS THE UPPER 
TROUGH DIGS OVER THE GREAT LAKES EARLY NEXT WEEK A COLD FRONT IS 
FORECAST TO ARRIVE ON MONDAY PROVIDING THE TRIGGER FOR MORE 
THUNDERSTORMS. SEVERE STORMS ARE A POSSIBILITY FROM SUNDAY INTO 
MONDAY.

THE FRONT IS FORECAST TO CLEAR THE AREA MONDAY NIGHT WHICH SHOULD 
ALLOW FOR DRYER AND MORE STABLE AIR TO OVERSPREAD THE AREA FROM THE 
NW ON TUESDAY. MAX TEMPS ARE FORECAST TO BE NEAR OR EVEN SLIGHTLY 
ABOVE CLIMO SAT THROUGH MONDAY...AND THEN BELOW CLIMO ON TUE BEHIND 
THE COLD FRONT

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...SHRA WILL LINGER A LITTLE LONGER NEAR THE AIRFIELD...SO 
WILL KEEP A SHORT VFR TEMPO WITH VRB WINDS. AFTER DISSIPATION... 
EXPECT A RETURN TO MORE STRATIFORM SCATTERED TO BROKEN CLOUD WITH 
BASES 1-2K FT. OVERNIGHT VISIBILITY WILL LOWER TO NEAR 6 MILES IN 
FOG AND HAZE VICINITY KCLT... BUT CONFIDENCE NOT YET SUFFICIENT TO 
FORECAST SIGNIFICANT RESTRICTIONS TOWARD DAYBREAK. GUIDANCE HAS 
BEGUN OT BACK OFF ON A PROLONGED PERIOD OF LOW CIGS LIKE THE LAST 
FEW DAYS. HOWEVER...GIVEN THE MOIST LOW LEVELS AND ONLY SLOWLY 
VEERING LOW LEVEL WINDS...WILL KEEP THE CURRENT MVFR CIGS AS IS WITH 
IMPROVEMENT OT LOW VFR BY NOON. THAT SAID...IT IS POSSIBLE THAT 
THERE WILL BE LITTLE IN THE WAY OF CIG RESTRICTIONS WHICH COULD LEAD 
TO MORE VSBY RESTRICTIONS AROUND DAYBREAK. SCT AFTERNOON CONVECTION 
WILL ONCE AGAIN DEVELOP...SO PROB30 ADVERTISED. NELY WINDS THIS 
EVENING BECOME CALM OVERNIGHT. SWLY WINDS DEVELOP DURING THE DAY 
WED. 

ELSEWHERE...SIMILAR CONDITIONS AND TRENDS TO KCLT. KAVL THE MAIN 
EXCEPTION WHERE VCTS WILL REMAIN POSSIBLE THRU EARLY EVENING. KAVL 
ALSO HAS A BETTER CHC OF IFR OVERNIGHT. LIGHT SLY WINDS AT KAVL 
BECOME CALM OVERNIGHT...THEN LIGHT NLY WED MORN THEN SLY FOR THE 
AFTERNOON. PROB30 ADVERTISED ALL LOCATIONS.

OUTLOOK... SHOWERS AND THUNDERSTORMS THURSDAY WITH THE PASSAGE OF A 
COLD FRONT. SCATTERED SHOWERS AND THUNDERSTORMS MAINLY DURING THE 
AFTERNOONS AND EVENINGS THROUGH THE END OF THE WEEK.

CONFIDENCE TABLE...

            02-08Z        08-14Z        14-20Z        20-02Z 
KCLT       MED   74%     MED   64%     MED   79%     HIGH 100%     
KGSP       MED   78%     MED   65%     MED   72%     HIGH 100%     
KAVL       HIGH  81%     MED   73%     MED   62%     MED   79%     
KHKY       MED   76%     MED   74%     HIGH  81%     HIGH 100%     
KGMU       MED   79%     MED   68%     MED   79%     HIGH 100%     
KAND       HIGH  80%     MED   70%     MED   72%     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...CSH
NEAR TERM...LGL/RWH
SHORT TERM...LG
LONG TERM...LG
AVIATION...RWH





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Weather Forecast Office Greenville-Spartanburg
GSP International Airport
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Page last modified: January 20, 2010

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