285
FXUS62 KGSP 041754
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
154 PM EDT MON AUG 4 2025
SYNOPSIS
COLD AIR DAMMING LINGERS THROUGH AT LEAST FRIDAY BEFORE A
POTENTIAL COASTAL LOW ERODES THE WEDGE THIS WEEKEND. BELOW NORMAL
HIGH TEMPERATURES THROUGH AT LEAST SATURDAY DESPITE A GRADUAL
WARMING TREND WEDNESDAY INTO THE WEEKEND. RAIN CHANCES REMAIN, WITH
THE POTENTIAL FOR LOCALLY HEAVY RAINFALL EACH DAY.
NEAR TERM /THROUGH TUESDAY/
AS OF 140 PM EDT MONDAY: DEEPENING UPPER TROUGH OVER THE MS VALLEY
WILL ACCOMPANY HEIGHT FALLS ACROSS THE AREA THROUGH THE FORECAST
PERIOD. AS A RESULT, DEEP LAYER SOUTH TO SOUTHWESTERLY FLOW WILL
OVERRUN THE REMNANT COLD POOL/IN-SITU CAD SURFACE DOME THAT'S
CURRENTLY IN PLACE AS DEEP GULF MOISTURE FILTERS IN PWAT VALUES
=> 2.00"+ ACROSS A GOOD PORTION OF THE FOOTHILLS AND PIEDMONT
OVERNIGHT TONIGHT INTO TUESDAY MORNING. GOOD ISENTROPIC LIFT TO
SUPPORT LOW-LEVEL CONVERGENCE AND UPPER DIVERGENCE THANKS TO THE
ENTRANCE REGION OF THE JET STREAK DRAPED OVERHEAD WILL HELP ENABLE
THE ONGOING CONVECTION TO OUR SOUTH THAT WILL WORK NORTH INTO THE
CWA LATER THIS EVENING, THROUGH THE OVERNIGHT PERIOD, AND PERSIST
INTO TUESDAY MORNING. VERY SATURATED PROFILES, DEEP WARM CLOUD
DEPTHS, AND STRONG FORCING FOR ASCENT WILL ESSENTIALLY SQUEEZE OUT
MOST OF THE RAIN POTENTIAL, ESPECIALLY ACROSS NORTHEAST GEORGIA,
UPSTATE SOUTH CAROLINA AND THE FAVORABLE UPSLOPE ZONES ALONG THE
BLUE RIDGE ESCARPMENT. THE ONE LIMITING FACTOR WILL BE THE LACK
OF INSTABILITY, WHICH WILL KEEP RAINFALL RATES FROM MAXIMIZING
THEIR FULL POTENTIAL. HOWEVER, STEADY RAINFALL RATES OVER A LONG
PERIOD OF TIME IS EXPECTED AND PER THE LATEST 12Z HREF ENSEMBLE
PROBABILITY MATCHED MEAN, THE AFOREMENTIONED CORRIDOR COULD PICK UP
BETWEEN 2-4" OF RAINFALL BY MID-MORNING TUESDAY, WITH A FEW
LOCATIONS EXCEEDING 4", MAINLY ALONG AND NORTH OF I-85. IN THIS
CASE, THE EXPANDED SLIGHT RISK FOR EXCESSIVE RAINFALL BY WPC IS
WARRANTED AS LOCALIZED INSTANCES OF FLASH FLOODING IS POSSIBLE. WITH
THE LACK OF INSTABILITY AND RECENT RAINFALL AMOUNTS ON THE LIGHTER
SIDE, DECIDED NOT TO GO FOR A FLOOD WATCH AT THIS TIME.
HIGH TEMPERATURES TODAY ARE VARIABLE AS LOCATIONS ALONG AND EAST
OF I-77 HAVE ADVECTED ENOUGH DRY AIR OUT OF THE NORTHEAST THAT THE
LOW CLOUDS STRUGGLED TO EXTEND THAT FAR INTO THE REGION. THIS HAS
ALLOWED FOR AFTERNOON HIGHS TO REACH INTO THE UPPER 70S AND A FEW
SPOTS HITTING THE 80F MARK. WHERE THE IN-SITU WEDGE IS STRONGEST
ACROSS MOST OF THE UPSTATE, NORTHEAST GEORGIA, AND BLUE RIDGE
MOUNTAINS, TEMPERATURES HAVE STRUGGLED TO GET OUT OF THE 60S WITH
PERSISTENT COVERAGE OF SCATTERED RAINFALL AND A STRONG LOW-LEVEL
CLOUD DECK. AS THE DEEPER MOISTURE TRANSPORTS INTO THE CWA LATER
THIS EVENING AND INTO TONIGHT, EXPECT THE CLOUD DECK AND PRECIP TO
EXPAND ACROSS THE REST OF THE CWA AS BETTER POPS ENTER THE REGION
WHEN THE FORCING IS STRONGEST. OVERNIGHT LOWS WILL REMAIN 4-8
DEGREES BELOW NORMAL AS THE CAD LOCKS IN AND IS REINFORCED BY WAA
OVERTOP THE COLD DOME AND A SECOND CANADIAN SURFACE HIGH WORKING
ITS WAY INTO NEW ENGLAND AND ATLANTIC CANADA. MODEL GUIDANCE
ARE KEEN ON KEEPING THE AXIS OF DEEPEST MOISTURE AND FORCING
ACROSS THE AREA ON TUESDAY AND GRADUALLY SHIFTS FROM WEST TO EAST
THROUGH TUESDAY AFTERNOON. THERE ARE SOME INSTANCES OF A COUPLE
HUNDRED J/KG OF MUCAPE, WHICH INCREASES THE THREAT FOR LOCALIZED
FLASH FLOODING IN LOCATIONS THAT RECEIVE HEAVY RAINFALL OVERNIGHT
TONIGHT. WITH THE IN-SITU CAD LOCKED IN ACROSS THE AREA AND VERY
LIKELY TO CATEGORICAL POPS IN PLACE, EXPECT AFTERNOON HIGHS FOR
TUESDAY TO RUN 15-20 DEGREES BELOW NORMAL.
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/
KEY MESSAGES:
1) COLD AIR DAMMING REMAINS AND KEEPS HIGH TEMPERATURES BELOW NORMAL.
2) RAIN CHANCES INCREASE THROUGH THE PERIOD, ESPECIALLY FOR THE
MOUNTAINS.
AS OF 125 PM EDT MONDAY: BY TUESDAY NIGHT, THE SYNOPTIC PATTERN IS
MOSTLY UNCHANGED FROM THE PREVIOUS FORECAST. SYNOPTICALLY, TWO AREAS
OF HIGH PRESSURE TO THE WEST AND EAST OF THE AREA REMAIN RELATIVELY
LOCKED INTO PLACE, WITH WEAK TROUGHING IN BETWEEN. AT THE SURFACE, A
STOUT AREA OF HIGH PRESSURE OVER THE NORTHEAST ALSO REMAINS PARKED
AND KEEPS THE COLD AIR DAMMING IN TACT. AS THE BERMUDA HIGH
CONTINUES TO RETREAT SLIGHTLY EAST, GUIDANCE REINFORCES A STRONG
SWATH OF MOISTURE ADVECTION WHICH PERSISTS THROUGH THE PERIOD.
GUIDANCE BRINGS IN PWATS APPROACHING THE 2 INCH MARK, ESPECIALLY
EAST OF THE MOUNTAINS THROUGH THURSDAY NIGHT. FOR THIS, NBM RETAINS
CATEGORICAL POPS (75-85%) ACROSS THE MOUNTAINS AND CHANCE (40-70%)
ELSEWHERE. THIS MAY BE SLIGHTLY OVERDONE, HOWEVER, GIVEN THE
CONTINUAL MOISTURE ADVECTION, ON AND OFF SHOWERS ARE LIKELY. THIS
COULD ALSO RAMP UP ISOLATED FLASH FLOODING WHERE AREAS HAVE BEEN
RECEIVING RAINFALL THE PAST FEW DAYS. THUNDER CHANCES SHOULD REMAIN
LOWER AS THE COLD AIR DAMMING KEEPS THE AREA MORE STABLE THAN IS
TYPICAL FOR THIS TIME OF YEAR. ANY BREAKS IN THE CLOUD COVER THOUGH
COULD INCREASE INSTABILITY AND RAISE THUNDER CHANCES. AS FAR AS
TEMPERATURES, THE HIGHS LOOK TO STAY BELOW NORMAL AND WELL BELOW THE
HOT 90S THE AREA HAS HAD THIS SUMMER. DEPENDING ON HOW MUCH THE CAD
CAN WEAKEN THROUGH THURSDAY, TEMPS COULD BE IN THE UPPER 70S TO LOW
80S BY THURSDAY.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
KEY MESSAGES
1) COLD AIR DAMMING LINGERS THROUGH AT LEAST FRIDAY.
2) A POTENTIAL COASTAL LOW COULD FORM THIS WEEKEND, INCREASING RAIN
AND THUNDERSTORM CHANCES.
3) TEMPERATURES SLOWLY INCREASE BUT REMAIN BELOW NORMAL.
AS OF 135 PM EDT MONDAY: LOOKING AHEAD, THE SYNOPTIC PATTERN DOESN'T
CHANGE MUCH AS AN UPPER HIGH STARTS TO DE-AMPLIFY OUT WEST AND THE
BERMUDA HIGH RETROGRADES FURTHER WESTWARD. LONG RANGE GUIDANCE SHOWS
THE WESTERN FRINGE OF THE HIGH REMAINS MOSTLY OVER THE SOUTHEAST,
KEEPING A FAIRLY MOIST PROFILE THROUGH THE END OF THE FORECAST
PERIOD. AT THE SURFACE, THERE IS SOME UNCERTAINTY AS TO HOW THE AREA
OF HIGH PRESSURE IN THE NORTHEAST EVOLVES. AT THIS TIME, A WEAK CAD
STARTS TO ERODE TOWARD FRIDAY AS THE HIGH GETS PINCHED OFF, BUT
COULD LINGER INTO SATURDAY. EITHER WAY, THE MOSTLY STABLE AIR MASS
STICKS AROUND FOR AT THE FIRST HALF OF THE EXTENDED FORECAST. BY
SATURDAY, THERE IS SOME GUIDANCE FROM THE GFS AND EURO THAT SUGGEST
A WEAK COASTAL LOW DEVELOPING OFF THE GA/CAROLINA COAST. CONFIDENCE
REMAINS LOW TO THIS DIRECTLY AFFECTING THE CWA GIVEN THE PERSISTENT
CAD IN PLACE. HOWEVER, WILL CONTINUE TO MONITOR AS THIS AREA IS
HIGHLIGHTED BY THE NATIONAL HURRICANE CENTER WITH A 30% OF
DEVELOPMENT. REGARDLESS, HIGH PWATS NEAR OR ABOVE THE 2 INCH MARK
AND SLOWLY INCREASING INSTABILITY BY THE WEEKEND, KEEPS THE POP
CHANCES ELEVATED THROUGH THE END OF THE PERIOD. TEMPERATURES LOOK TO
SLOWLY WARM THROUGH THE EXTENDED, BUT ARE HIGHLY DEPENDENT ON THE
CAD AND WHEN IT ERODES. SO EXPECT TEMPS TO REMAIN JUST BELOW THE
NORMAL RANGE BY THE END OF THE WEEKEND.
AVIATION /18Z MONDAY THROUGH SATURDAY/
AT KCLT AND ELSEWHERE: SCATTERED SHOWERS AND ASSOCIATED
RESTRICTIONS CONTINUE TO PUSH ACROSS KAVL AND UPSTATE TAF SITES THIS
AFTERNOON. EXPECT THIS ACTIVITY TO REACH KCLT AND KHKY LATER THIS
EVENING. MOST TERMINALS WILL MAINTAIN AN MVFR VSBY/CIG RESTRICTIONS
EITHER PREVAILING OR THROUGH A TEMPO/PROB30 FOR THIS AFTERNOON AND
EVENING. HEAVIER RAINFALL IS EXPECTED ACROSS MUCH OF THE AREA
OVERNIGHT THROUGH TUESDAY MORNING. LIFR/IFR CIGS AND IFR/MVFR VSBYS
WILL ACCOMPANY THE AREA OF HEAVIER RAINFALL AND SHOULD STICK AROUND
THROUGH THE END OF THE FORECAST PERIOD. WITH THAT BEING SAID,
DECIDED TO GO WITH PREVAILING -SHRA AND IFR OR LOWER CIGS THROUGH
THE 18Z TAF PERIOD, WITH KCLT LIFTING TO MVFR BY PEAK HEATING
TUESDAY. NORTHEASTERLY WINDS (5-10 KTS) WILL PERSIST THROUGH MUCH OF
THE PERIOD, WHILE KAVL MAINTAINS A SOUTH-SOUTHEASTERLY (4-8 KTS)
WIND.
OUTLOOK: PRECIP CHANCES REMAIN ELEVATED INTO TUESDAY. ALTHOUGH
TEMPERATURES ONLY GRADUALLY WARM BACK UP OVER THE REMAINDER OF THE
WEEK, PRECIPITATION CHANCES TREND TOWARD A MORE TYPICAL SUMMERTIME
REGIME BY WEDNESDAY WITH CHANCES MAINLY IN THE AFTERNOONS AND EARLY
EVENINGS. PERIODIC RESTRICTIONS REMAIN POSSIBLE THRU LATE WEEK,
ESPECIALLY OVERNIGHT AND IN THE MORNING.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...CP
NEAR TERM...CAC
SHORT TERM...CP
LONG TERM...CP
AVIATION...CAC
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