567
FXUS62 KGSP 141743
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
143 PM EDT SUN SEP 14 2025
SYNOPSIS
DRY HIGH PRESSURE REMAINS OVER THE REGION THROUGH MONDAY. A
DEVELOPING LOW PRESSURE SYSTEM ALONG THE CAROLINA COAST MAY BRING
RAIN TO OUR AREA FOR THE MIDDLE OF THE WEEK. DRY HIGH PRESSURE
RETURNS FOR THE LAST HALF OF THE WEEK.
NEAR TERM /THROUGH MONDAY/
AS OF 100 PM SUNDAY, KEY MESSAGES:
1. MOST LIKELY, ALL AREAS WILL REMAIN DRY THROUGH TONIGHT, WITH
TEMPERATURES SLIGHTLY ABOVE NORMAL.
2. INCREASING CLOUD COVER OVERNIGHT INTO MORNING, WITH ISOLATED
SHOWERS OVER THE MOUNTAINS MONDAY AFTERNOON.
3. SLIGHTLY COOLER IN MOST AREAS NORTHEAST OF I-26 MONDAY OWING
TO CLOUD COVER.
EXPECTING A QUIET AFTERNOON WEATHER-WISE, WITH CUMULUS NOW FIRING
OVER THE MOUNTAINS BUT APPEARING SHALLOW, REFLECTING SUBSIDENCE
INVERSION. SOME CIRRUS ARE BEGINNING TO SPREAD INLAND ON THE
PERIPHERY OF A SURFACE LOW IN THE OPEN ATLANTIC, SOUTH OF THE OUTER
BANKS. AN UPPER LOW NOW NEAR JACKSONVILLE IS IN THE PROCESS OF
SHEARING OFF OF THE UPPER TROUGH DRIFTING OFF THE EAST COAST. THE
SFC LOW WILL DRIFT NORTH, PROMOTING LOW TO MIDLEVEL MOISTURE
ADVECTION ACROSS MUCH OF NC BY LATE MONDAY MORNING. THE UPPER LOW
WILL DRIFT SLIGHTLY NORTHWARD, AND A VORT LOBE IS PROGGED TO ROUND
IT AND LEAD TO DPVA SHIFTING EAST TO WEST ACROSS THE CAROLINAS
LATE TONIGHT THRU MONDAY. TOGETHER, THESE DEVELOPMENTS SHOULD BRING
INCREASED HIGH ALTITUDE CLOUD COVER BEGINNING IN THE PREDAWN HOURS,
LIKELY JOINED BY LOWER CLOUD DECKS AFTER DAYBREAK. THE SUBSIDENCE
INVERSION WEAKENS SUCH THAT DIURNAL MOUNTAIN CONVECTION APPEARS
POSSIBLE MONDAY, WITH ENSUING EASTERLY UPSLOPE FLOW AND THE DPVA
ENHANCING LIFT. A SLIGHT-CHANCE OR ISOLATED PRECIP MENTION RETURNS
ALONG THE BLUE RIDGE ESCARPMENT, WITH MEAN FLOW VECTORS SUGGESTING
ANY PROPAGATION WOULD BE TOWARD THE WEST OR SOUTHWEST FROM THERE.
INCREASING CLOUDS TONIGHT REDUCE CONFIDENCE IN MOUNTAIN VALLEY FOG
POTENTIAL, ALTHOUGH OVERALL SOME AREAS OF FOG ARE STILL LIKELY;
THINKING IS FOG MAY JUST NOT BE AS LONG-LIVED AS IT WAS THE
LAST COUPLE OF MORNINGS. CLOUD COVER AND/OR WEAK CAA ON NE FLOW
IS EXPECTED TO BRING MAX TEMPS BACK A LITTLE BELOW NORMAL OVER
THE NC PIEDMONT AND ADJACENT AREAS, BUT IN THE SUNNIER WESTERN
MOUNTAINS AND SOUTHERN GA/SC ZONES, TEMPS SHOULD BE ABOUT THE SAME
AS SUNDAY'S.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/
AS OF 1:25 PM EDT SUNDAY: THE SHORT-TERM FCST PICKS UP AT 00Z ON
TUESDAY WITH A REX BLOCK IN PLACE OVER MOST OF THE EASTERN CONUS.
THIS BLOCKING PATTERN IS EXPECTED TO LINGER OVER OUR REGION THRU
THE SHORT-TERM PERIOD, ALTHOUGH IT DOES GRADUALLY BREAK DOWN/ISSI-
PATE AS THE PERIOD WEARS ON. AT THE SURFACE, BROAD CANADIAN HIGH
PRESSURE WILL BE CENTERED NORTH OF NEW ENGLAND AS THE PERIOD BEGINS
LATE MONDAY. AT THE SAME TIME, ANOTHER WEAK SFC LOW WILL HAVE DEDE-
LOPED JUST OFF THE CAROLINA COAST AND BE SPREADING SOME AMOUNT OF
ATLANTIC MOISTURE OVER THE CAROLINAS. OVER THE NEXT COUPLE OF DAYS
MOST OF THE LATEST MODEL GUIDANCE HAS THE LOW GRADUALLY MOVING OVER
THE NC COAST AND REMAINING THERE THRU THE END OF THE PERIOD LATE WED.
OVERALL, NO MAJOR CHANGES WERE MADE TO THE FCST WITH A SLIGHT CHANCE
FOR PRECIP ACROSS MOST OF OUR FCST AREA ON TUESDAY AND A SOLID CHANCE
OVER PORTIONS OF THE NC MTNS AND INTO THE FOOTHILLS AND PIEDMONT. ON
WEDNESDAY, PRECIP CHANCES HAVE TRENDED LOWER WITH ONLY A SLIGHT CHANCE
NOW FCST FOR PORTIONS OF THE NC MTNS. NO EXCESSIVE QPF IS ANTICIPATED.
HIGH TEMPERATURES HAVE TRENDED A BIT COOLER ON TUESDAY, ESPECIALLY
OVER OUR NE ZONES WHERE MORE CLOUD COVER AND STRONGER NLY FLOW IS
EXPECTED. TEMPS ARE WARMER ON WEDNESDAY BUT STILL EXPECTED TO BE A
FEW DEGREES BELOW NORMAL FOR MID-SEPTEMBER.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
AS OF 1:15 PM EDT SUNDAY: THE EXTENDED FORECAST PICKS UP AT 00Z ON
THURSDAY WITH WHAT'S LEFT OF A REX-TYPE BLOCKING PATTERN LINGERING
OVER THE EASTERN CONUS. BY LATE THURSDAY, MOST OF THE LATEST GUIDANCE
HAS THE REX BLOCK DISSIPATED. ON FRIDAY, BROAD UPPER TROFING WILL
AMPLIFY OVER SOUTHERN QUEBEC AS ANOTHER CLOSED UPPER LOW DEVELOPS
WEST OF THE GREAT LAKES. OVER THE WEEKEND, THIS UPPER LOW IS EXPEC-
TED TO DRIFT EASTWARD, YET IT WILL LIKELY REMAIN WELL TO OUR NORTH
AS FLAT UPPER RIDGING PERSISTS OVER THE SOUTHEAST AND MID-ATLANTIC.
AT THE SFC, WEAK LOW PRESSURE WILL BE CENTERED SOMEWHERE OVER THE
MID-ATLANTIC COAST AS THE PERIOD BEGINS LATE WEDNESDAY. ON THURSDAY,
THIS SYSTEM WILL LIFT FURTHER NE AND DISSIPATE. OVER THE NEXT COUPLE
OF DAYS, ANOTHER SFC LOW IS EXPECTED TO DEVELOP SOMEWHERE OVER THE
NORTHERN PLAINS AND EVENTUALLY MOVE A WEAK COLD FRONT TOWARDS OUR
AREA. IT REMAINS UNCLEAR WHEN THIS FRONT WILL ACTUALLY REACH OUR
FCST AREA AND HOW MUCH IMPACT IT WILL HAVE ON OUR SENSIBLE WX. THIS
IS PARTLY BECAUSE MOST OF THE LONG-RANGE GUIDANCE HAS ANOTHER ROBUST
CANADIAN HIGH MIGRATING SE OVER THE WEEKEND. IT'S NOT CLEAR HOW FAR
SOUTH THIS HIGH WILL SPREAD AND HOW MUCH IT WILL IMPACT THE APPROACH
OF THE ABOVE-MENTIONED COLD FRONT. REGARDLESS, THE FIRST HALF OF THE
PERIOD HAS TRENDED DRIER WITH DIURNALLY-DRIVEN SLIGHT CHANCE POPS OVER
THE NC MTNS ON THURSDAY AND FRIDAY AND SOLID CHANCES FOR PRECIP ACROSS
MOST OF OUR FCST AREA OVER THE WEEKEND. TEMPERATURES START OUT A FEW
DEGREES ABOVE NORMAL ON THURSDAY AND REMAIN ABOVE NORMAL THRU SATURDAY.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: VFR THRU THE PERIOD ASIDE FROM MOUNTAIN
VALLEY FOG. PATCHY DIURNAL CU AND CIRRUS WILL BE SEEN THIS AFTN,
WITH CIRRUS INCREASING IN COVERAGE OVERNIGHT AS SFC/UPPER LOWS
DRIFT NORTH NEAR THE SOUTHEAST COAST. THE CIRRUS PROBABLY WILL
NOT BE ENOUGH TO INHIBIT FOG FORMATION IN THE VALLEYS OR AT KAVL,
BUT CONFIDENCE IS REDUCED ENOUGH TO PUT IFR ONLY IN A 2-HR TEMPO
AT DAYBREAK. PREVAILING NE'LY FLOW DURING DAYTIME HOURS WITH MORE
RURAL SITES SEEING CALM OR VRB OVERNIGHT. KCLT MAY TOGGLE TO A
NEAR DUE-EAST WIND AROUND OR AFTER SUNSET BUT NE STILL APPEARS
MORE LIKELY. SPOTTY DIURNAL CUMULUS RETURN MON MORNING WITH WINDS
LIKELY BEGINNING TO GUST AT KCLT WITH STRONGER WINDS DEVELOPING
ALOFT AROUND OFFSHORE SFC LOW.
OUTLOOK: MOSTLY VFR OUTSIDE OF MORNING MOUNTAIN VALLEY FOG AND LOW
STRATUS THROUGH AT LEAST TUESDAY. RAIN CHANCES INCREASE ACROSS THE
TERMINALS MONDAY NIGHT, POSSIBLY LINGERING INTO MID TO LATE WEEK,
BUT CONFIDENCE IS LOW.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...DEO
NEAR TERM...WIMBERLEY
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...WIMBERLEY
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