811
FXUS62 KGSP 020027
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
827 PM EDT FRI AUG 1 2025
SYNOPSIS
ONE LAST HOT AND HUMID DAY ON TAP WITH WIDESPREAD SHOWERS AND
THUNDERSTORMS DEVELOPING THROUGH THIS EVENING. A FEW STRONG TO
SEVERE STORMS, AS WELL AS ISOLATED FLASH FLOODING, WILL BE POSSIBLE
WITH TODAY'S DIURNAL ACTIVITY. COLD AIR DAMMING DEVELOPS THIS
WEEKEND AND LINGERS INTO THE NEW WORKWEEK BRINGING MUCH NEEDED
RELIEF FROM THE HEAT AND HUMIDITY IN THE FORM OF COOLER AND BELOW
NORMAL HIGH TEMPERATURES. SHOWER AND THUNDERSTORM CHANCES STICK
AROUND THROUGH NEXT WEEK BUT A LULL MAY DEVELOP SUNDAY INTO MONDAY.
NEAR TERM /THROUGH SATURDAY/
AS OF 1250 PM FRIDAY: THE LAST OF THE REMNANT LOW CLOUDINESS WAS
FINALLY EXITING THE FCST AREA, WHILE CONVECTIVE INITIATION HAS
TAKEN PLACE OVER THE RIDGES AS EXPECTED. THE DEVELOPMENT HAS BEEN
GRADUAL AS HAS BEEN OUR DESTABILIZATION, BUT WE'RE ON OUR WAY WITH
SFC-BASED CAPE UP INTO THE 2000-3000 J/KG RANGE. THE DCAPE HAS BEEN
MODEST AT BEST, BUT WATER VAPOR IMAGERY HAS A POCKET OF SOMEWHAT
DRIER AIR EAST OF THE MTNS, SO THE EXPECTATION REMAINS THAT IT WOULD
BE SUFFICIENT TO SUPPORT SOME STRONGER DOWNDRAFTS AND OUTFLOWS. THE
WIND SHIFT BOUNDARY WAS ALREADY SINKING SOUTH ACROSS THE UPSTATE AND
NORTHEAST GEORGIA, BUT THE EFFECTIVE FRONT WAS STILL LOCATED TO THE
NORTH OF THE FORECAST AREA. NO SIGNIFICANT CHANGES ARE NOTED WITH
THE DAY 1 CONVECTIVE OUTLOOK UPDATE KEEPING MOST OF THE FCST AREA
IN A MARGINAL RISK FOR DAMAGING WIND GUSTS. THE 12Z HREF AND THE
MORNING RUNS OF THE HRRR CONTINUE TO SUPPORT THE IDEA THAT WE WILL
HAVE JUST ENOUGH SHEAR TO PROMOTE SOME MULTICELL ORGANIZATION ON
COLD POOL MERGERS AND OUTFLOWS. IF WE CAN GET THE STORMS ORGANIZED
AS THEY MOVE EAST OFF THE BLUE RIDGE AS IS HINTED BY THE HREF,
OUR CHANCES OF SEVERE WIND GUSTS WILL GO UP. THERE'S ALSO THE
RISK OF EXCESSIVE RAINFALL THAT EXTENDS INTO THE EVENING HOURS,
WHAT WITH VERY DEEP WARM CLOUD POTENTIAL AND PRECIPITABLE WATER
WELL OVER TWO INCHES. THE CONCERN WILL BE ANCHORING OF STORMS
NEAR THE BLUE RIDGE ESCARPMENT BECAUSE OF EASTERLY LOW LEVEL
FLOW OPPOSING THE WESTERLY MID/UPPER FLOW, OR MULTIPLE ROUNDS OF
STORMS OVER THE SAME AREA. A FLOOD WATCH HAS BEEN CONTEMPLATED,
BUT THE EXPECTATION AT THIS MOMENT IS FOR ONLY ISOLATED/LOCALIZED
THREATS. OH YEAH, AND TODAY WILL BE THE LAST HOT DAY. NO CHANGES
TO THE HEAT ADVISORY OVER THE LAKELANDS.
THE EFFECTIVE COLD FRONT SHOULD DROP SOUTHWARD ACROSS THE FORECAST
AREA LATE THIS EVENING BEHIND THE MAIN DEEP CONVECTION, AND IN
BEHIND, THE LOW LEVEL NORTHEASTERLY FLOW WILL IMPROVE. THERE SHOULD
BE ENOUGH MOISTURE LEFT OVER TO BE RUN UPSLOPE ON THE EAST SIDE OF
THE MTNS TO FORCE ADDITIONAL SHOWERS WELL INTO THE OVERNIGHT NEAR
THE ESCARPMENT IN NC, AS THE EFFECTIVE FRONT OOZES S AND SW ACROSS
THE UPSTATE INTO NORTHEAST GA. THAT SHOULD KEEP RAIN CHANCES IN
PLAY FOR MOST OF THE REGION WITH PERHAPS THE EXCEPTION OF THE NW
PIEDMONT WHERE THE DRY AIR ARRIVES FIRST. LOW TEMPS WILL STILL BE
NEAR NORMAL.
SATURDAY IS ANOTHER TRICKY DAY AS THE GUIDANCE CONTINUES TO SHOW
A NASCENT COLD AIR DAMMING WEDGE EARLY IN THE DAY. THE PARENT HIGH
MOVING EAST OVER THE GREAT LAKES LOOKS RELATIVELY WEAK, BUT THE LOW
LEVEL NORTHEASTERLY FLOW HAS SUFFICIENT LOW LEVEL MOISTURE TO KEEP
A THICK CLOUD DECK UNDERNEATH THE DEVELOPING INVERSION. HOW FAR THE
WEDGE BOUNDARY MAKES IT WILL HAVE A BIG IMPACT ON THE WEATHER. SOME
OF THE GUIDANCE STALLS THE FRONT OVER THE SOUTHWEST PART OF THE
FCST AREA THROUGH THE DAY, PROVIDING ENOUGH FORCING TO PRODUCE
NUMEROUS SHOWERS, BUT THE CAMS IN THE 12Z HREF ARE RELATIVELY QUIET,
SUGGESTING THAT BOUNDARY CLEARS THE FCST AREA EARLY IN THE DAY. THE
FCST FOLLOWS THE NBM AND MAINTAINS A RELATIVELY HIGH PRECIP PROB,
BUT NOT WITHOUT A HEALTHY DOSE OF SKEPTICISM ABOUT THE EXTENT OF
THE PRECIP. EITHER WAY, THE CLOUDS SHOULD KEEP US FROM BEING ABLE
TO WARM UP MUCH AND HIGH TEMPS SHOULD STRUGGLE TO GET OUT OF THE
70S. THE DOWNWARD TREND IN TEMPS CONTINUES. IF THE PRECIP DOESN'T
DEVELOP, WE MIGHT BE MORE LIKE UPPER 70S THAN THE MID 70S WE WILL
HAVE IN THE FORECAST. IT WILL FEEL A WHOLE LOT DIFFERENT THAN THE
LAST MONTH, THAT'S FOR SURE...
SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/
AS OF 108 PM EDT FRIDAY: WEAK, BROAD CYCLONIC FLOW ALOFT OVER
THE EASTERN CONUS WILL LINGER THROUGH MUCH OF THE FORECAST
PERIOD. ~1024MB SURFACE HIGH WILL SET UP SHOP OVER THE NORTHEASTERN
CONUS BY SATURDAY AS THE NEAR-TERM FRONT SAGS SOUTH OF THE
CFWA. DRIER SURFACE AIR FROM THE NORTHEAST WILL HELP TO SET
THE STAGE FOR A HYBRID CAD EVENT THROUGH THE WEEKEND INTO THE
EARLY PARTS OF NEXT WEEK. THE LATEST SREF SHOWS A LI BETWEEN
3-5 INDICATING THAT THE STATIC STABILITY IS RELATIVELY STRONG
FOR THE TIME OF YEAR, ESPECIALLY IN REGARDS TO A SUMMERTIME CAD
EVENT. ONGOING SCATTERED SHOWERS ARE LIKELY SATURDAY NIGHT AS
A DECENT ATLANTIC FETCH (850MB WIND: ESE @ 15-20 KTS) FILTERS IN
ATOP THE CAD DOME TO GO ALONG WITH BETTER ISENTROPIC LIFT. EXTENSIVE
CLOUD COVER AND ELEVATED PRECIP CHANCES WILL ALLOW FOR OVERNIGHT LOWS
TO RUN A FEW DEGREES BELOW NORMAL. A SHORTWAVE IS SEEN ROUNDING
THE BASE OF AFOREMENTIONED CYCLONIC FLOW ALOFT, WHILE DRIER AIR
CONTINUES TO NOSE IN FROM THE NORTHEAST BY SUNDAY. THE WEDGE
BOUNDARY WILL BE FAR SOUTH OF THE AREA AND ESSENTIALLY CHOKE ANY
REALLY DEEP MOISTURE FLUX FROM FILTERING INTO THE REGION. IN THIS
CASE, PRECIP COVERAGE WILL BE LESS, WITH THE SOUTHWEST MOUNTAINS
AND UPPER SAVANNAH RIVER VALLEY BEING THE MOST LIKELY LOCATIONS OF
RECEIVING RAINFALL DUE TO THE CLOSER PROXIMITY TO THE BOUNDARY. SOME
FORM OF SCATTERED SHOWERS IS SHOWN PER MODEL GUIDANCE OF BREAKING
CONTAINMENT FURTHER NORTH IN THE CWA. CLOUD COVER WILL REMAIN
EXTENSIVE AS THE AREA REMAINS LOCKED INTO THE CAD PATTERN. AS
A RESULT, AFTERNOON HIGHS ON SUNDAY SHOULD END UP 12-18 DEGREES
BELOW NORMAL, BRINGING IN MUCH NEEDED RELIEF FROM THE HEAT.
NOT TOO MUCH OF A PATTERN CHANGE ON MONDAY, BUT PARENT HIGH SLIPS
FURTHER OFFSHORE INTO THE NORTHERN ATLANTIC, WHILE THE AREA WILL
BE UNDER MORE OF AN IN-SITU CAD. MODEL TRENDS ARE DRIER FOR SUNDAY
NIGHT INTO THE DAYTIME PERIOD MONDAY. A DIGGING SHORTWAVE TROUGH
IS SHOWN OVER THE CENTRAL CONUS BY MONDAY AFTERNOON, ALLOWING THE
FLOW ALOFT TO BECOME MORE SOUTH TO SOUTHWESTERLY. THIS IS TURN
WILL ENHANCE THE MOISTURE FLUX PROVIDED BY THE STALLED BOUNDARY
TO THE SOUTH AND GRADUALLY WORK NORTH. THIS SHOULD ALLOW FOR
MORE SCATTERED SHOWERS TO WORK INTO THE AREA, BUT NOT GROWING IN
COVERAGE UNTIL LATER MONDAY. IN THESE TYPES OF SETUPS, SCATTERED
SHOWERS ARE POSSIBLE THROUGHOUT THE DURATION OF A CAD, WHICH IS
WHY MENTIONABLE POPS REMAIN IN THE FORECAST THROUGH THE FORECAST
PERIOD. SREF AND DETERMINISTIC GUIDANCE ARE NOT EXCITED WITH ANY
ELEVATED INSTABILITY, SO ONLY STRATIFORM PRECIP IS EXPECTED OUTSIDE
OF A ROGUE THUNDERSTORM THROUGH THE SHORT TERM. SOME CHANGES ARE ON
THE HORIZON DURING THE EXTENDED PERIOD, BUT THE CAD DOME REMAINS
LOCKED IN THROUGH MONDAY AS AFTERNOON HIGHS WILL RUN 8-12 DEGREES
BELOW NORMAL AS SOME PEAKS OF SUNSHINE MAY START MAKING IT TO THE
SURFACE.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
AS OF 143 PM EDT FRIDAY: UPPER TROUGH WILL SHIFT TOWARDS THE EASTERN
THIRD OF THE CONUS, WHILE A SURFACE HIGH BECOMES REINFORCED OVER NEW
ENGLAND AND ATLANTIC CANADA LATER TUESDAY INTO WEDNESDAY. THIS WILL
HELP TO KEEP THE SURFACE COOL LAYER IN PLACE AND STATIC STABILITY
HIGH AS THE LI REMAINS NEAR A VALUE OF 3-5 THROUGH MUCH OF THE
WORKWEEK, EMPHASIZING A LINGERING CAD EVENT. BETTER MOISTURE FLUX
WILL REACH THE AREA BY TUESDAY AS THE FLOW ABOVE THE SURFACE TURNS
SOUTHERLY BEING ON THE LEESIDE OF THE UPPER TROUGH AS IT SLOWLY
TRAVELS FURTHER EAST. IN THIS CASE, POPS WILL RAMP BACK BUT NOT
EXCITED ABOUT THE THUNDERSTORM POTENTIAL AS THERE IS ONLY SOME FORM
OF ELEVATED INSTABILITY. HOWEVER, THIS IS THE SUMMERTIME SO YOU CAN
NEVER TRULY RULE IT OUT. THE ATLANTIC SUBTROPICAL RIDGE WILL BEGIN
TO DEEPEN BY THE LATTER HALF OF THE PERIOD, WHILE THE RIDGE OVER
THE SOUTHWESTERN CONUS AIDS IN THE WEAKNESS OF THE TROUGH OVER THE
SOUTHEASTERN CONUS. THIS WILL ALLOW FOR MORE DIURNAL CONVECTIVE,
ESPECIALLY OVER THE MOUNTAINS BY THE END OF THE FORECAST PERIOD AND
FOR A GRADUAL WARMING TREND TO OCCUR. THE CAD IS SHOWN ERODING BY
LATE INTO THE WORKWEEK THROUGH EITHER A COASTAL LOW OR SURFACE WIND
DIVERGENCE PER MODEL GUIDANCE. TEMPERATURES REMAIN A CATEGORY OR
TWO BELOW NORMAL, ESPECIALLY DURING THE DAYTIME PERIOD THROUGH D7.
AVIATION /01Z SATURDAY THROUGH WEDNESDAY/
AT KCLT AND ELSEWHERE: AT PRESENT, WE'VE STILL GOT SOME LARGE
CLUSTERS OF SHOWERS AND THUNDERSTORMS ACROSS OUR AREA. THIS
ACTIVITY WILL LIKELY CONTINUE THRU LATE TONIGHT, THUS I HAVE
EITHER A PROB30 OR A TEMPO FOR TSRA THRU ROUGHLY 04Z AT ALL
TAF SITES. AFTER THAT, I KEEP A VCSH AT MOST TERMINALS INTO
THE OVERNIGHT FOR LINGERING SHOWERS. AT THE SAME TIME, CIGS
ARE EXPECTED TO LOWER TO IFR ACROSS OUR FCST AREA AND REMAIN
IFR THRU THE REST OF THE TAF PERIOD FOR THE UPSTATE TERMINALS
AND KAVL. THERE'S A DECENT CHANCE THAT CIGS WILL LIFT TO MVFR
AT KCLT AND KHKY BY MID TO LATE AFTERNOON TOMORROW, WITH KCLT
IMPROVING TO VFR BY ROUGHLY 00Z TOMORROW EVENING. IN ADDITION,
MOST SITES HAVE MVFR VISBY RESTRICTIONS BEGINNING OVERNIGHT AND
LINGERING THRU MUCH OF TOMORROW. THEY ALSO HAVE PROB30S FOR SHRA
TOMORROW AFTN/EVENING, WITH SOME AMOUNT OF MOIST UPGLIDE EXPECTED
OVER THE CAD. THUNDER/LIGHTNING APPEARS UNLIKELY AS INSTABILITY
WILL BE LACKING OVER THE AREA. OUTSIDE THE MTNS, MOST SITES ARE
ALREADY REPORTING NELY WINDS WITH WINDS AT KAVL EXPECTED TO FAVOR
AN ELY DIRECTION THRU MOST OF THE TAF PERIOD. THE OTHER TERMINALS
SHOULD REMAIN NELY THRU THE END OF THE PERIOD.
OUTLOOK: WIDESPREAD CIG RESTRICTIONS MAY LINGER INTO EARLY SUNDAY.
OTHERWISE, THE REST OF THE WEEKEND LOOKS VFR APART FROM THE USUAL
LOW STRATUS AND/OR FOG EACH MORNING. SCT TO NUMEROUS SHOWERS WILL
BE POSSIBLE AGAIN ON SUNDAY, ESPECIALLY OVER THE MTNS AND WESTERN
SC UPSTATE. A RETURN TO MORE TYPICAL SUMMERTIME WEATHER IS EXPECTED
EARLY NEXT WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...CAC
NEAR TERM...JPT/PM
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...JPT
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