549
FXUS62 KGSP 041833
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
233 PM EDT TUE AUG 4 2026
WHAT HAS CHANGED
NO MAJOR CHANGES TO THINKING, BUT REDEFINED THE PERIODS COVERED
BY EACH KEY MESSAGE.
KEY MESSAGES
1. ABOVE-AVERAGE RAIN CHANCES AND BELOW NORMAL TEMPERATURES
CONTINUE THROUGH WEDNESDAY.
2. A MORE TYPICAL LATE SUMMER PATTERN RETURNS THURSDAY,
THOUGH TEMPERATURES REMAIN SLIGHTLY BELOW NORMAL AND DAILY
CHANCES FOR SHOWERS AND STORMS WILL REMAIN ELEVATED THROUGH
SATURDAY. TEMPERATURES AND PRECIPITATION CHANCES RETURN TO AROUND
NORMAL SUNDAY AND MONDAY.
DISCUSSION
KEY MESSAGE 1: ABOVE-AVERAGE RAIN CHANCES AND BELOW NORMAL
TEMPERATURES CONTINUE THROUGH WEDNESDAY.
AN UPPER LOW IS CENTERED OVER NORTHERN GEORGIA AS OF 2 PM TUE WILL
DRIFT SLOWLY NORTHWARD THROUGH WEDNESDAY, PROMOTING EASTERLY FLOW
IN THE LOW- TO MID-LEVELS, WHICH HAS BROUGHT A PLUME OF ENHANCED
PWATS FROM THE ATLANTIC INTO WESTERN NC AND THE EASTERN UPSTATE,
THOUGH THE REMAINDER OF THE CWA REMAINS MOIST AT THE SURFACE
DESPITE DRY AIR BEING PRESENT ALOFT WITHIN THE CYCLONE. LCLS ARE
LOW, AND 700-500MB LAPSE RATES ARE A LITTLE BETTER THAN USUAL, SO
WITH DIURNAL HEATING ALREADY HAVING PRODUCED 2000+ J/KG SBCAPE,
A BROAD AREA OF SHOWERS WITH EMBEDDED STORMS HAS ALREADY BECOME
ESTABLISHED, CENTERED ON THE PIEDMONT. STORM MOTION HAS BEEN SLOW
AND A NUMBER OF OBS SITES HAVE RECEIVED A QUICK 1 TO 2 INCHES
OF RAIN. WE WILL BE CLOSELY MONITORING FOR POTENTIAL LOCALIZED
FLASH FLOODING. DCAPE IS STRONGEST NEAR THE CORE OF THE LOW, OVER
THE WESTERN UPSTATE AND NE GA, AND AN ISOLATED SEVERE MICROBURST
THREAT DOES EXIST PARTICULARLY IN THAT AREA. WHAT STEERING FLOW
THERE IS SHOULD GENERALLY PUSH THE CONVECTION TOWARD THE NORTH
OR NORTHWEST. CAMS LARGELY DEPICT THE ACTIVITY PROPAGATING IN
THAT DIRECTION BUT VARY AS TO WHETHER A SECOND ROUND DEVELOPS IN
THE WAKE OF THE CURRENT ACTIVITY. WHILE OUTFLOWS HAVE LED TO SOME
POCKETS OF STABILIZATION, THE EARLY START, SOUPY DEWPOINTS IN THE
LOWER 70S, AND STRONG ANVIL-LEVEL FLOW SUGGESTING A RELATIVELY LOW
CHANCE THAT CIRRUS WILL FILL IN AND PRECLUDE REDEVELOPMENT. THUS
WE RETAIN AT LEAST 20-40% POPS UNTIL MIDNIGHT OVER MUCH OF THE
PIEDMONT. EASTERLY NEAR-SURFACE FLOW SUGGESTS STRATUS MAY ADVECT
IN FROM THE ATLANTIC TOWARD DAYBREAK, BUT RADIATION FOG/STRATUS
COULD ALSO OCCUR WITH SO MUCH OF THE AREA GETTING SOAKED THIS
AFTERNOON AND SFC WINDS BEING LIGHT TONIGHT.
WEDNESDAY, THE UPPER LOW FILLS AND IS REABSORBED INTO
THE WESTERLIES. SURFACE WINDS FAVOR SOUTHERLY AGAIN; PWATS
INCREASE ACROSS THE BOARD WITH THE DRYING EFFECT OF THE UPPER
LOW NO LONGER BEING A FACTOR. IN GENERAL THIS DISTRIBUTES POPS
MORE CLIMATOLOGICALLY, WITH THE GREATEST VALUES BEING OVER THE
MOUNTAINS/FOOTHILLS. LAPSE RATES JUST ABOVE THE BOUNDARY LAYER ARE
SLIGHTLY BETTER, AND WITH THE HIGHER PWATS ABOVE-CLIMO CHANCES
ARE WARRANTED (50-80% IN MUCH OF THE CWA). 500MB WINDS WILL BE
STRONGER WHICH MAY RESULT IN A LITTLE BETTER 0-6KM BULK SHEAR,
BUT DCAPE SHOULD BE LOWER, SO THAT WILL HELP MITIGATE ANY DAMAGING
WIND THREAT. STORMS MAY JUST HAVE A SLIGHTLY BETTER CHANCE OF
FORMING INTO CLUSTERS.
IN THE SOUTHERLY FLOW REGIME, TEMPS WEDNESDAY INCH BACK INTO
THE MID-80S OVER MOST OF THE PIEDMONT, PARTICULARLY SOUTH OF
I-85. HOWEVER ALL VALUES SHOULD REMAIN A BIT BELOW NORMAL.
KEY MESSAGE 2: A MORE TYPICAL LATE SUMMER PATTERN RETURNS THURSDAY,
THOUGH TEMPERATURES REMAIN SLIGHTLY BELOW NORMAL AND DAILY
CHANCES FOR SHOWERS AND STORMS WILL REMAIN ELEVATED THROUGH
SATURDAY. TEMPERATURES AND PRECIPITATION CHANCES RETURN TO AROUND
NORMAL SUNDAY AND MONDAY.
FOLLOWING THE DISSOLUTION OF THE UPPER LOW, OUR WEATHER PATTERN
RETURNS TO BEING MORE TYPICAL FOR THIS TIME OF YEAR; THAT IS TO
SAY, BECOMING MORE ILL-DEFINED. PWAT VALUES FROM THE GFS AND ECMWF
ENSEMBLES REMAIN JUST ON THE WET SIDE OF CLIMO. DIURNAL INSTABILITY
WILL REMAIN THE PRIMARY DRIVER OF SHOWER/THUNDERSTORM CHANCES,
AND AN UPWARD TREND IN SBCAPE GENERALLY LOOKS TO OCCUR THURSDAY
AND FRIDAY, WITH VALUES REMAINING SIMILAR OR MARGINALLY HIGHER ON
SATURDAY. A LONGWAVE TROUGH SLOWLY MOVES ACROSS THE MISSISSIPPI
VALLEY INTO THE GREAT LAKES REGION WHILE THE BERMUDA HIGH REMAINS
STRONG IN THE WESTERN ATLANTIC. THIS WILL REINFORCE A SOUTHERLY
LOW-LEVEL FLOW REGIME AND ABOVE-CLIMO POPS ACROSS THE AREA, WITH
70-80% CHANCES EACH DAY OVER THE MOUNTAINS AND 30-50% FOR THE
PIEDMONT. SHEAR WILL BE WEAK, AND A MARGINALLY SEVERE MICROBURST
CAN'T BE RULED OUT ANY DAY, THOUGH THE DAMAGING WIND THREAT
DOES NOT LOOK PARTICULARLY NOTABLE. BY SUNDAY THE AFOREMENTIONED
TROUGH LOOKS TO HAVE FLATTENED OUT AND/OR SHIFTED EAST SUCH THAT
HEIGHT RISES OCCUR IN THE OHIO VALLEY, AND LOW-LEVEL FLOW TURNS
MORE WESTERLY AGAIN. HENCE, POPS FALL BACK TO A MORE TYPICAL
30-60% FOR THE MOUNTAINS AND 10-30% FOR THE PIEDMONT THAT DAY
AND MONDAY. TEMPS TREND BACK TO NEAR NORMAL, WITH LOWER PIEDMONT
LOCATIONS FLIRTING WITH 90 SUNDAY AND MOST PIEDMONT AREAS RISING
INTO THE LOWER 90S MONDAY.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
AT KCLT AND ELSEWHERE: SCT SHRA/TSRA ALREADY ONGOING AROUND THE
TERMINAL AREA AS OF 1730Z TUE, WHICH PROMPTED INCLUSION OF TEMPOS
IN ALL TAFS TO BEGIN THE PERIOD. HIGH MOISTURE AND SLOW STORM
MOTION SUGGESTS IFR VSBY LIKELY WITH ANY TSRA, AND GUSTS UP TO
25 KT ARE A REASONABLE EXPECTATION. LCLS WILL REMAIN LOW AND VFR
MAY NOT PREVAIL UNTIL VERY LATE AFTERNOON. EXPECTING THE AREA TO
BE WORKED OVER TO SOME DEGREE BY 22Z BUT CAN'T RULE OUT AT LEAST
ISOLATED REDEVELOPMENT THROUGH EVENING. THUS VCSH USED LIBERALLY
AFTER 22Z. EASTERLY ONSHORE FLOW LOOKS TO BRING DAYBREAK STRATUS
OVER KCLT/KHKY IF NOT THE SC SITES, BUT THE SC SITES AND KAVL
APPEAR TO BE AT RISK OF RADIATION FOG/STRATUS ALSO. THUS HAVE
PREVAILING IFR OR LIFR DEVELOPING BETWEEN 04-05Z AND DAYBREAK AT
ALL SITES. WINDS REMAIN LARGELY NE WHEN NOT VRB OR CALM THROUGH
TONIGHT, EXCEPT KAVL WHICH REMAINS SE THRU THE PERIOD. AFTER
MORNING STRATUS/FOG DISSIPATE WED, WINDS SHOULD PICK UP FROM THE
SE TO S. LCLS NOT EXPECTED TO BE QUITE AS LOW THOUGH DIURNAL CU
MAY FORM AT MVFR LEVEL AND SO RESTRICTIONS ARE SLOW TO ERODE. KAVL
GETS A PROB30 FOR DIURNAL TSRA BY 16Z WED AND KCLT GETS VCSH FOR
WED AFTN, WITH LOWER CONFIDENCE THERE.
OUTLOOK: SCATTERED, MAINLY AFTERNOON SHOWERS AND THUNDERSTORMS WILL
CONTINUE THROUGH THE REMAINDER OF THE WEEK, WITH ASSOCIATED BRIEF
FLIGHT RESTRICTIONS. PATCHY FOG AND LOW STRATUS WILL BE POSSIBLE
EACH MORNING, ESPECIALLY IN THE MOUNTAIN VALLEYS AND ANYWHERE THAT
HEAVIER RAINFALL HAS DEVELOPED THE PREVIOUS EVENING.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
JCW
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