538
FXUS62 KGSP 050611
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
211 AM EDT TUE AUG 5 2025
SYNOPSIS
A WEDGE OF COOL AND MOIST AIR LINGERS THROUGH MUCH OF THE
WEEK BEFORE A POTENTIAL COASTAL LOW ERODES THE WEDGE THIS
WEEKEND. ALTHOUGH A WARMING TREND IS EXPECTED TO BEGIN WEDNESDAY,
BELOW NORMAL HIGH TEMPERATURES ARE EXPECTED TO CONTINUE THROUGH
AT LEAST SATURDAY. RAIN CHANCES REMAIN, WITH THE POTENTIAL FOR
LOCALLY HEAVY RAINFALL EACH DAY.
NEAR TERM /THROUGH TONIGHT/
AS OF 200 AM EDT TUESDAY...
KEY MESSAGES:
1) WELL BELOW NORMAL HIGH TEMPS EXPECTED AGAIN TODAY THANKS TO COLD
AIR DAMMING
2) WIDESPREAD RAIN EXPECTED THROUGH AT LEAST THIS AFTERNOON
3) LOCALLY HEAVY RAINFALL MAY LEAD TO ISOLATED AREAS OF FLASH
FLOODING
THE SOUTHWESTERN PERIPHERY OF A SFC HIGH WILL CONTINUE TO NOSE DOWN
INTO THE SOUTHERN APPALACHIANS THROUGHOUT THE NEAR TERM KEEPING COLD
AIR DAMMING AROUND. WITH MULTIPLE SHORTWAVES EXPECTED TO LIFT
NORTHEAST ACROSS THE WESTERN CAROLINAS AND NORTHEAST GEORGIA THROUGH
TONIGHT, RAIN WILL STICK AROUND THROUGH AT LEAST THIS AFTERNOON. A
BRIEF LULL MAY DEVELOP THIS EVENING BEFORE ANOTHER ROUND DEVELOPS
TONIGHT INTO EARLY WEDNESDAY MORNING BUT CONFIDENCE IS LOW. WITH CAD
EXPECTED TO LIMIT INSTABILITY AGAIN TODAY, EMBEDDED THUNDER SHOULD
BE HARD TO COME BY. HOWEVER, A FEW OF THE CAMS DEPICT SOME MUCAPE
DEVELOPING ACROSS THE SW NC MOUNTAINS AND THE FAR SE FRINGE OF THE
FORECAST AREA DURING PEAK HEATING THIS AFTERNOON SO MAINTAINED
CHANCE THUNDER ACROSS THESE AREAS. OTHERWISE, THUNDER IS NOT EXPECTED
FOR THE REMAINDER OF THE FORECAST AREA. THE MAIN CONCERN DURING THE
NEAR TERM WILL BE THE POTENTIAL FOR EXCESSIVE RAINFALL. WITH WET
ANTECEDENT CONDITIONS IN PLACE AND WITH RAINFALL TOTALS EXPECTED TO
SLOWLY PILE UP THROUGH TONIGHT, LOCALLY HEAVY RAINFALL MAY LEAD TO
ISOLATED AREAS OF FLASH FLOODING. OPTED NOT TO ISSUE A FLOOD WATCH
AS THE LACK OF INSTABILITY WILL LIMIT RAIN RATES AND DUE TO THE FACT
THAT ANY FLASH FLOODING CONCERNS WILL REMAIN ISOLATED. RAINFALL
AMOUNTS FROM 1-2.5 INCHES CAN BE EXPECTED ACROSS MUCH OF THE
FORECAST AREA THROUGH THE NEAR TERM, WITH LOWER AMOUNTS EXPECTED
ACROSS THE NC MOUNTAINS (OUTSIDE OF THE FAVORED E/SE UPSLOPE AREAS).
PER USUAL, LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE AND WILL BE
HIGHLY DEPENDENT ON WHERE HEAVIER DOWNPOURS DEVELOP. CAD WILL ONCE
AGAIN ALLOW FOR WELL BELOW NORMAL TEMPS THIS AFTERNOON. HIGHS WILL
STRUGGLE TO REACH INTO THE LOW TO MID 70S EAST OF THE MOUNTAINS AND
THE LOWER 60S TO MID 70S ACROSS THE MOUNTAINS. THESE FORECAST TEMP
VALUES WILL LEAD TO HIGH AROUND 13-18 DEGREES BELOW NORMAL FOR MOST
LOCATIONS. MOSTLY CLOUDY SKIES AS WELL AS PERSISTENT RAIN MAY
FURTHER LIMIT HOW WARM WE GET TODAY SO HIGHS COULD END UP A FEW
DEGREES COOLER THAN FORECAST.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
KEY MESSAGES:
1) COLD AIR DAMMING REMAINS AND KEEPS HIGH TEMPERATURES BELOW
NORMAL.
2) RAIN CHANCES CONTINUE THROUGH THE PERIOD, ALTHOUGH THE POTENTIAL
FOR ORGANIZED AREAS OF PRECIP...WITH A TRANSITION TO MORE OF A
DIURNALLY-DRIVEN CONVECTIVE REGIME IS EXPECTED.
AS OF 110 AM EDT TUESDAY: THE UPPER TROUGH ACROSS THE DEEP SOUTH
AND TENN VALLEY WILL CONTINUE TO DRIFT EAST AND WEAKEN THROUGH
THE SHORT TERM, WITH A RESULTANT WEAKENING OF WIND FIELDS/UPSLOPE
& ISENTROPIC FLOW. OVERALL SUPPORT FOR ORGANIZED AREAS OF PRECIP
IMPACTING THE FORECAST AREA WILL THEREFORE STEADILY DECREASE DURING
THE MID-WEEK PERIOD, WITH A DIMINISHING POP TREND. MEANWHILE,
THE UPPER FLOW OVER THE NORTHEAST CONUS AND SOUTHEAST CANADA
WILL REMAIN BROADLY CONFLUENT THROUGH THE PERIOD, WITH SURFACE
HIGH PRESSURE EXPECTED TO MOVE ONLY SLOWLY ACROSS NEW ENGLAND AND
SOUTHERN QUEBEC, SUPPORTING INVERTED RIDGING AND CONTINUED...ALBEIT
WEAKENING COLD AIR DAMMING ON THE EAST SIDE OF THE APPALACHIANS
THROUGH THE PERIOD. THIS WILL LIMIT DIURNAL DESTABILIZATION ACROSS
THE HEART OF OUR CWA THROUGH THE PERIOD, ALTHOUGH SOME DEGREE OF
INSTABILITY IS EXPECTED ALONG THE SOUTHERN AND WESTERN PERIPHERY OF
THE AREA EACH AFTERNOON. THEREFORE, THE HIGHEST CHANCES FOR SHOWERS,
ALONG WITH INCREASING CHANCES FOR THUNDERSTORMS (POPS OF 50-60% WED
AND THU AFTERNOON) WILL BE IN THESE AREAS...ALTHOUGH MOISTURE WILL
BE SUFFICIENT TO ADVERTISE CHANCE POPS ACROSS THE INTERIOR OF THE
CWA AS WELL. TEMPERATURES WILL STEADILY MODERATE DUE TO WEAKENING
CAD AS WELL AS A LACK OF WIDESPREAD/PERSISTENT PRECIPITATION TO
REINFORCE THE COLD POOL. NEVERTHELESS, CLOUD COVER AND E/NE LOW
LEVEL FLOW WILL RESULT IN HIGH TEMPERATURES REMAINING A SOLID 10+
DEGREES BELOW CLIMO IN MOST AREAS.
LONG TERM /FRIDAY THROUGH MONDAY/
KEY MESSAGES
1) WEAKENING COLD AIR DAMMING LINGERS THROUGH AT LEAST SATURDAY.
2) CONFIDENCE IS LOW REGARDING POTENTIAL COASTAL LOW IMPACTS
THIS WEEKEND.
3) FORECAST TEMPERATURES SLOWLY INCREASE BUT REMAIN BELOW NORMAL
UNTIL AT LEAST MONDAY.
AS OF 130 AM EDT TUESDAY: THE UPPER TROUGH JUST WEST OF THE FORECAST
AREA WILL CONTINUE TO WEAKEN DURING THE EARLY PART OF THE EXTENDED,
EVOLVING INTO MORE OF A WEAKNESS IN A RE-ASCENDANT SUBTROPICAL
RIDGE OVER THE WEEKEND. INVERTED SURFACE RIDGING WILL REMAIN IN
PLACE ON THE EAST SIDE OF THE APPALACHIANS THROUGH THE WEEKEND,
ALBEIT IN A WEAKENING STATE AS PARENT SURFACE HIGH PRESSURE
DRIFTS SOUTHEAST OFF THE NEW ENGLAND COAST. GLOBAL MODEL GUIDANCE
REMAINS IN GENERALLY GOOD AGREEMENT IN SPINNING UP A WEAK TROPICAL
DISTURBANCE SOMEWHERE NEAR THE CAROLINA COAST DURING THE WEEKEND,
ALTHOUGH THEY DIFFER GREATLY IN TERMS OF POSITION AND EVENTUAL
TRACK. LOW LEVEL FLOW RESPONDING TO THIS FEATURE WILL LIKELY BE
THE FINAL DEATH KNELL FOR COLD AIR DAMMING ACROSS OUR AREA, AND
DEPENDING UPON THE TRACK OF THE LOW, COULD RESULT IN DEEPENING
NE FLOW THAT DRIES OUT THE FORECAST AREA DURING THE LATTER HALF
OF THE PERIOD. OR...THE LOW COULD MOVE INLAND (AS DEPICTED BY
THE 12Z ECMWF) AND BRING ABOUT THE POTENTIAL RETURN OF WIDESPREAD
PRECIP TO AT LEAST A PORTION OF THE CWA. IN LIGHT OF THE INHERENT
UNCERTAINTY, POPS AND TEMPS ARE ALLOWED TO TREND TOWARD CLIMATOLOGY
DURING THE LATTER HALF OF THE EXTENDED, WITH GENERALLY SCATTERED,
MOSTLY DIURNAL CONVECTION ADVERTISED EACH DAY, AND A STEADY WARMING
TREND CULMINATING IN FORECAST MAX TEMPS FALLING ONLY A DEGREE OR
SO OF CLIMO BY DAY 7/MONDAY.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
AT KCLT AND ELSEWHERE: COLD AIR DAMMING WILL REMAIN IN PLACE THROUGH
06Z TAF PERIOD KEEPING RAIN AND RESTRICTIONS AROUND WITH VERY LITTLE
IMPROVEMENT EXPECTED. THIS WILL ALSO ALLOW WINDS TO REMAIN NE EAST
OF THE MOUNTAINS AND E/SE WINDS ACROSS THE MOUNTAINS. CIGS ARE
MOSTLY RANGING FROM VFR TO IFR AS OF 06Z. CIGS ARE EXPECTED TO
GRADUALLY LOWER OVER THE NEXT FEW HOURS LEADING TO GENERALLY IFR
CIGS EXPECTED THROUGHOUT MOST OF THE TAF PERIOD. KCLT COULD SEE CIGS
LIFT TO MVFR LEVELS TOWARDS THE END OF THE TAF PERIOD BUT CONFIDENCE
IS LOW. AS OF 06Z VSBYS ARE RANGING FROM IFR TO MVFR AND THESE
RESTRICTION LEVELS ARE GENERALLY EXPECTED TO HOLD THROUGHOUT THE TAF
PERIOD. PERIODS OF RA OR +RA COULD LEAD TO SLIGHT OR BRIEF
IMPROVEMENT OF CIGS AND VSBYS, POSSIBLY GOING MVFR OR VFR AT TIMES.
HOWEVER, CONFIDENCE ON THIS WAS TOO LOW TO MENTION IN THE TAFS AT
THIS TIME. COULD SEE A BRIEF WINDOW OF DRIER CONDITIONS TOWARDS THE
END OF THE TAF PERIOD BEFORE RAIN CHANCES INCREASE AGAIN. WITH THE
KGMU ASOS OFFLINE, WILL NOT PLAN ON AMENDING THE TAF UNTIL OBS START
FLOWING AGAIN.
OUTLOOK: DRIER CONDITIONS MAY RETURN WEDNESDAY INTO WEDNESDAY NIGHT.
COLD AIR DAMMING STICKS AROUND THROUGH THE WORKWEEK KEEPING RAIN
CHANCES AS WELL AS PERIODIC RESTRICTIONS AROUND. EMBEDDED
THUNDERSTORMS WILL BE POSSIBLE EACH AFTERNOON AND EVENING BUT
CONFIDENCE IS LOW.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...JDL
NEAR TERM...AR
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...AR
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