337
FXUS62 KGSP 081829
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
229 PM EDT WED OCT 8 2025
SYNOPSIS
COOL AND DRY HIGH PRESSURE CONTROLS OUR WEATHER FOR THURSDAY AND
FRIDAY WITH BELOW NORMAL TEMPERATURES. THIS HIGH PRESSURE MOVES
OFF THE EAST COAST LATE FRIDAY WITH A WARMING TREND OVER THE
WEEKEND AND INTO EARLY NEXT WEEK. AN UPPER LEVEL RIDGE DEVELOPS
OVER THE LOWER MISSISSIPPI VALLEY NEXT WEEK.
NEAR TERM /THROUGH THURSDAY/
AS OF 215 PM EDT WEDNESDAY: A COLD FRONT CONTINUES TO PUSH
SOUTHEAST ACROSS THE FORECAST AREA THIS AFTERNOON, NOW LOCATED
SOUTH OF I-85 AND INTO THE LOWER PIEDMONT. THE BOUNDARY IS
MARKED BY A WIND SHIFT FROM SOUTHWEST TO NORTH-NORTHWEST AND A
NARROW BAND OF LOW-TOPPED OR WEAK SHOWERS SUPPORTED BY BOUNDARY-
LAYER CONVERGENCE. DEEPER CONVECTION IS CONFINED TO AREAS
FARTHER SOUTH WHERE MIXED-LAYER CAPE EXCEEDS 500 J/KG, NOW SOUTH
OF OUR CWA. AS A RESULT, THE MENTION OF THUNDERSTORMS ACROSS
THE LOWER PIEDMONT HAS BEEN DROPPED WITH THE MORE FAVORABLE
THERMODYNAMIC ENVIRONMENT SHIFTING SOUTHWARD.
CAM GUIDANCE SUGGESTS SOME ADDITIONAL POST-FRONTAL CONVECTIVE
DEVELOPMENT LATE THIS AFTERNOON INTO EARLY EVENING, MAINLY TO THE
LEE OF THE BLUE RIDGE IN THE FOOTHILLS AND WESTERN PIEDMONT. THIS
ACTIVITY WILL BE SUPPORTED BY DIFFERENTIAL POSITIVE VORTICITY
ADVECTION (DPVA) ACCOMPANYING AN UPPER SHORTWAVE TROUGH AND BY
LOW- LEVEL SPEED CONVERGENCE ALONG THE ADVANCING NORTHERLY FLOW
AND PRESSURE SURGE BEHIND THE FRONT. ISOLATED SHOWERS REMAIN IN
THE FORECAST, BUT THUNDER WAS REMOVED FROM THE NBM OUTPUT, AS
INSTABILITY BECOMES INCREASINGLY SHALLOW WITH DRY AIR ADVECTION
AND THE LOSS OF SURFACE HEATING.
DESPITE THE FRONTAL PASSAGE, AMPLE SUNSHINE AND A DEEP BOUNDARY
LAYER WILL OFFSET WEAK COLD AIR ADVECTION (CAA), ALLOWING HIGHS TO
REACH THE 60S-70S ACROSS THE NC MOUNTAINS AND LOWER 80S ELSEWHERE.
TONIGHT, A STRONG PRESSURE RISE COUPLET AND ENHANCED CAA WILL
ACCOMPANY HIGH PRESSURE BUILDING SOUTHWARD FROM THE GREAT LAKES.
NORTHERLY TO NORTHEASTERLY WINDS WILL INCREASE TO 10-15 MPH WITH
GUSTS 20-30 MPH OVERNIGHT. LOWS WILL RANGE FROM THE 40S IN THE
NORTHERN NC MOUNTAINS TO THE UPPER 50S IN THE GA AND SC PIEDMONT.
MINIMUM WIND CHILLS IN THE 30S ARE EXPECTED AT THE HIGHEST
ELEVATIONS SUCH AS MOUNT MITCHELL. SKY COVER WAS TRENDED MORE
PESSIMISTIC BY BLENDING TOWARD THE NBM 75TH PERCENTILE, GIVEN
A STRONG SIGNAL FOR STRATOCU TRAPPED BENEATH THE POST-FRONTAL
SUBSIDENCE INVERSION.
CLOUDS SHOULD GRADUALLY ERODE FROM NORTHEAST TO SOUTHWEST THROUGH
THURSDAY MORNING AS DRIER AIR DEEPENS. HOWEVER, RENEWED CLOUD
DEVELOPMENT MAY OCCUR ACROSS THE GEORGIA MOUNTAINS AND PORTIONS
OF THE CENTRAL AND SOUTHERN NC MOUNTAINS WHERE AN INVERTED TROUGH
DEVELOPS ALONG THE WESTERN SLOPES AHEAD OF AN APPROACHING MID-LEVEL
SHORTWAVE TROUGH. HIGHS THURSDAY WILL RANGE FROM THE 60S IN THE
MOUNTAINS TO THE 70S ACROSS THE PIEDMONT, CONSISTENT WITH NBM
GUIDANCE.
SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY/
AS OF 1250 PM EDT WEDNESDAY...
KEY MESSAGES:
2) BREEZY WINDS EXPECTED, ESPECIALLY EAST OF THE MOUNTAINS
3) FROST POSSIBLE THURSDAY NIGHT INTO EARLY FRIDAY MORNING ACROSS
PORTIONS OF THE NORTH CAROLINA MOUNTAINS
WE SHOULD STILL BE IN THE THROES OF A DRY COLD AIR DAMMING WEDGE
THURSDAY NIGHT AND FRIDAY, COURTESY OF A COOL PARENT SFC HIGH MOVING
ACROSS THE NORTHEAST AND OFF THE NEW ENGLAND COAST. WINDS WILL
REMAIN BREEZY ACROSS THE AREA EAST OF THE MTNS WITH A WELL-MIXED
BUT SHALLOW BOUNDARY LAYER UNDERNEATH A STRONG SUBSIDENCE INVERSION,
BUT WINDS WILL BE NOWHERE NEAR ADVISORY LEVEL. WHAT IS INTERESTING
IS THAT THE TOP OF THIS INVERSION LAYER WILL BE AROUND 4K-6K FEET
AND THE WINDS ALOFT AT THE TOP OF THE INVERSION WILL BE QUITE A
BIT WEAKER. TEMPS EARLY FRIDAY MORNING WILL BE ON THE ORDER OF
5-10 DEGREES BELOW NORMAL OVER THE MTNS, AND DOWN INTO THE 30S
ABOVE 4K FEET. THE RELATIVELY LIGHT WIND RAISES THE POTENTIAL FOR
FROST DEVELOPMENT IN THE PRE-DAWN HOURS FRIDAY MAINLY OVER THE
NRN MOUNTAINS OF NC. HOWEVER, THE POTENTIAL FOR CLOUDS AT/BELOW
THE INVERSION COULD SNEAK INTO THE MTNS AND KEEP THE TEMPS HIGHER
THAN FCST. GUIDANCE HAS SHOWN SOME MINOR FLUCTUATIONS OVER THE
PAST FEW CYCLES, SO THERE IS NO CLEAR TREND. SUFFICE TO SAY,
THERE'S SOME POTENTIAL FOR A FROST ADVISORY FOR THE NRN MOUNTAINS,
BUT WE WILL GET A FEW MORE LOOKS AT IT.
WHILE ALL THAT IS HAPPENING, A WEAK MID/UPPER LOW WILL DRIFT ACROSS
THE SOUTHEAST AND BEGIN TO INTERACT WITH THE OLD FRONTAL BOUNDARY TO
OUR SOUTH FRIDAY INTO SATURDAY. IT MAY TAKE AWHILE, BUT EVENTUALLY
THIS MID/UPPER LOW WILL INDUCE CYCLOGENESIS OFFSHORE OF GA/SC AND
ALONG THE FRONT FRIDAY NIGHT INTO SATURDAY. SIZABLE DIFFERENCES
REMAIN IN HOW THE MODELS HANDLE HOW QUICKLY THIS LOW INTERACTS
WITH AN UPPER LOW DROPPING DOWN ACROSS THE GREAT LAKES AND PULLS
IT NORTHWARD AND HOW CLOSE IT WILL BE TO THE COAST, BUT THE
MAJORITY OF SOLUTIONS KEEP THE WESTERN EDGE OF THE PRECIP
ASSOCIATED WITH THE LOW JUST TO THE EAST OF THE FCST AREA THRU
SUNDAY. INSTEAD, WE ARE LEFT WITH A REMNANT DRY AND SOMEWHAT
COOL POOL AS THE LOWS CUT US OFF FROM THE OLD PARENT HIGH. THE
AIR MASS SHOULD MODIFY THROUGH THE WEEKEND WITH TEMPS REBOUNDING
TOWARD NORMAL AND MOST OF US GETTING FAIR WEATHER.
LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/
AS OF 1224 PM EDT WEDNESDAY...IT WOULD APPEAR THAT N OR NW FLOW
ALOFT WILL REIGN SUPREME FOR THE FIRST HALF OF NEXT WEEK, ACCORDING
TO MOST OF THE MODEL GUIDANCE. ALTHO THERE ARE DIFFERENCES BETWEEN
MODEL SOLUTIONS REGARDING THE STRENGTH AND TRACK OF THE UPPER LOW
DROPPING DOWN ACROSS THE MID-ATLANTIC REGION FROM THE NORTHWEST,
AND THUS HOW CLOSE IN PROXIMITY THE LOW WILL PASS RELATIVE TO
THE WESTERN CAROLINAS, THE NET RESULT WILL MOST LIKELY BE THE
SAME. WITHOUT MUCH IN THE WAY OF MOISTURE TO WORK WITH, THERE
WON'T BE ANYTHING FOR THE FORCING ASSOCIATED WITH THE LOW PASSAGE
TO ACT UPON ON SUNDAY NIGHT AND MONDAY. THE DEPARTING LOW MAY KEEP
A CYCLONIC FLOW ALOFT LINGERING INTO TUESDAY, BUT STILL WE WOULD
BE ON THE DRY SIDE OF THE SYSTEM. NOTE THAT THE GFS SUGGESTS A
RIBBON OF LOW LEVEL MOISTURE RUNNING UP INTO THE MTNS, BUT THE
CHANCES OF MEANINGFUL PRECIP LOOK REALLY SMALL AND NOT WORTH
MENTIONING AT THIS POINT. BY WEDNESDAY, THE FLOW BACKS TO MORE
NORTHWESTERLY AS WE COME MORE UNDER THE INFLUENCE OF AN UPSTREAM
RIDGE THAT SUPPORTS HIGH PRESSURE TO OUR NORTH. THE UPSHOT IS
THAT WE HAVE A DRY FORECAST THROUGH THE FIRST HALF OF NEXT WEEK,
WITH TEMPS SLOWLY RETURNING TO SOMETHING CLOSE TO NORMAL, OR MAYBE
A FEW DEGREES WARMER THAN AVERAGE.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
AT KCLT AND ELSEWHERE: A COLD FRONT PASSED THROUGH THE TERMINALS
THIS TERMINALS THIS MORNING. WINDS HAVE ALREADY SHIFTED OUT OF
THE N (VARYING BETWEEN NW AND NE). WIND SPEEDS SHOULD GENERALLY BE
BETWEEN 5-10 KT THROUGH THE REST OF THIS AFTERNOON EXCEPT HIGHER
AT KAVL (10-15 KT WITH GUSTS TO 25 KT) WHERE A STRONG POST-FRONTAL
PRESSURE SURGE HAS ARRIVED. POST-FRONTAL SHOWERS MAY DEVELOP LATE
THIS AFTERNOON BEFORE DIMINISHES AFTER SUNSET WITH THE LOSS OF
DAYTIME HEATING. CAMS SHOW THIS ISOLATED CONVECTION MOST LIKELY
TO DEVELOP IN THE FOOTHILLS, INCLUDING IN VICINITY OF GSP, GMU,
AND AND. ASIDE FROM A BRIEF/LOCAL RESTRICTIONS POSSIBLE WITH
THIS LATE-DAY ACTIVITY, THERE IS HIGH CONFIDENCE IN VFR THROUGH
THE VALID TAF PERIOD. WINDS WILL WEAKEN AT KAVL AFTER SUNSET THIS
EVENING WHILE INCREASE ELSEWHERE AS THE RAPID PRESSURE RISES SHIFT
DOWNSTREAM. GUST TO 25 KT ARE POSSIBLE TONIGHT AT MOST TERMINALS. NE
WINDS WILL CONTINUE INTO THURSDAY WITH GUSTS GRADUALLY LOWERING
TO 15-20 KT BY LATE MORNING AND THE AFTERNOON.
OUTLOOK: DRIER CONDITIONS PERSIST FOR THE REMAINDER OF THE WEEK
AND INTO THE WEEKEND. PATCHY MORNING FOG/LOW STRATUS WILL BE
POSSIBLE IN THE MOUNTAIN VALLEYS EACH DAY, OTHERWISE VFR
CONDITIONS EXPECTED.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...DEO
NEAR TERM...JK
SHORT TERM...PM
LONG TERM...AR/PM
AVIATION...JK
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