375
FXUS62 KGSP 290517
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
117 AM EDT TUE SEP 29 2026
WHAT HAS CHANGED
TIMING OF RAINFALL HAS SLOWED ONCE AGAIN FOR THE END OF THE WEEK.
CONFIDENCE CONTINUES TO INCREASE THAT FRIDAY WILL REMAIN MOSTLY DRY,
WITH RAIN ARRIVING BY SATURDAY.
TEMPERATURES WERE LOWERED A TAD FOR SUNDAY AND BEYOND.
THE AVIATION DISCUSSION WAS UPDATED FOR THE 06Z TAF ISSUANCE.
KEY MESSAGES
1. FOLLOWING A PROTRACTED PERIOD OF CLEAR, DRY WEATHER, ACCOMPANIED
BY A SLOW BUT STEADY WARMING TREND LASTING MOST OF THIS WEEK, THE
SIGNAL IS GETTING STRONGER FOR COLD-AIR DAMMING TO DEVELOP OVER
THE WEEKEND. CLOUDS AND RAIN ARE EXPECTED TO RETURN BY SATURDAY,
AND A STRONG COOLING TREND MAY BE IN STORE BY SUNDAY.
DISCUSSION
KEY MESSAGE 1: FOLLOWING A PROTRACTED PERIOD OF CLEAR, DRY WEATHER,
ACCOMPANIED BY A SLOW BUT STEADY WARMING TREND LASTING MOST OF
THIS WEEK, THE SIGNAL IS GETTING STRONGER FOR COLD-AIR DAMMING TO
DEVELOP OVER THE WEEKEND. CLOUDS AND RAIN ARE EXPECTED TO RETURN
BY SATURDAY, AND A STRONG COOLING TREND MAY BE IN STORE BY SUNDAY.
WITH A WEAKENING COASTAL LOW NOW CENTERED OVER THE NANTUCKET/CAPE
COD REGION AND CONTINUING ITS NORTHEASTWARD MARCH, LOW-LEVEL
NORTHWESTERLY CAA HAS DIMINISHED SOMEWHAT ACROSS THE CAROLINAS,
LEAVING US IN AN INCREASINGLY STAGNANT PATTERN. THE MOST RECENT
UPPER-AIR ANALYSIS FEATURES A BROAD Z500 RIDGE AXIS EXTENDING FROM
THE SOUTHERN GREAT PLAINS, ACROSS THE OZARKS, AND INTO THE GREAT
LAKES, WITH WEAK NORTHWESTERLY FLOW DRAPED ACROSS THE CAROLINAS.
WATER VAPOR IMAGERY DEPICTS A DRY CYCLONIC CIRCULATION CENTERED
OVER THE APPALACHIANS...BUT THINK THAT'LL PASS WITH LITTLE FANFARE
TONIGHT, OTHER THAN PERHAPS LENDING AN EXTRA TWINKLE TO THE STARS.
THE FORECAST REMAINS MUCH THE SAME AS IT HAS FOR DAYS; UPPER RIDGING
IS STILL EXPECTED TO BUILD ACROSS THE SOUTHEAST OVER THE NEXT 24
HOURS OR SO, WHILE AT THE SURFACE BROAD, ILL-DEFINED HIGH PRESSURE
WILL MIGRATE OFF THE ATLANTIC COAST THROUGH THE MIDDLE OF THE
WEEK, OPENING THE CAROLINAS UP TO WEAK MOISTURE RETURN BY THURSDAY
AND FRIDAY. SOME UNCERTAINTY REMAINS IN HOW QUICKLY LOW-LEVEL
UPGLIDE WILL BEGIN TO PRODUCE RAINFALL AGAIN...BUT LONG-RANGE
ENSEMBLES CONTINUE TO TREND MORE AND MORE TOWARD A LATER ONSET,
WITH SOME 75% OF THE MOST RECENT LREF ENSEMBLE MEMBERS NOW HOLDING
RAIN OFF UNTIL, AT THE EARLIEST, FRIDAY NIGHT. ALL THREE OF THE
GLOBAL DETERMINISTIC MODELS NOW HOLD RAIN OFF UNTIL EARLY SATURDAY.
HAVING SAID ALL THAT, IT STILL LOOKS LIKE A GOOD CASE FOR A HYBRID
COLD AIR DAMMING SETUP, WITH INCIPIENT HIGH PRESSURE DRAPED ACROSS
THE NORTHEAST FRIDAY AND SATURDAY CONTRIBUTING A SYNOPTIC COMPONENT
AND THE ONSET OF RAINFALL PROVIDING A STRONG DIABATIC COMPONENT.
STILL THINK, THEREFORE, THAT A CAD WEDGE IS LIKELY TO DEVELOP
OVER THE WEEKEND. IT SHOULD BE SHORT-LIVED, HOWEVER, AS GUIDANCE
REMAINS IN EXCELLENT AGREEMENT (FOR THIS TIMESCALE) ON THE ARRIVAL
OF A STRONG COLD FRONT BY MONDAY AFTERNOON, USHERING IN A COOL CP
AIR MASS BY THE END OF FORECAST PERIOD. ACCORDINGLY, THE LATEST
FORECAST FEATURES CLOUDY SKIES AND A STRONG COOLING TREND OVER THE
WEEKEND...WITH HIGHS IN THE 70S BY SUNDAY AND MONDAY...AND LOWS
APPROACHING THEIR COOLEST SO FAR THIS FALL TO START OUT NEXT WEEK.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
AT KCLT AND ELSEWHERE: EXPECT DRY, VFR CONDITIONS TO CONTINUE THRU
THE 06Z TAF PERIOD. BKN VFR STRATOCU IS CURRENTLY SCATTERING OVER
OUR NC PIEDMONT ZONES AND SHOULD MOSTLY DISSIPATE OVER THE NEXT FEW
HRS. MTN VALLEY FOG/LOW STRATUS WILL LIKELY DEVELOP AGAIN OVERNIGHT
IN THE USUAL LOCATIONS, BUT IT'S NOT EXPECTED TO IMPACT KAVL. WINDS
WILL BE LIGHT THRU THE TAF PERIOD (GENERALLY 5 KTS OR LESS). THEY
WILL CONTINUE TO FAVOR A N TO NE DIRECTION, BUT WILL BE LIGHT AND
VRB TO CALM AT TIMES THRU THE DAY/EVENING.
OUTLOOK: DRY, VFR CONDITIONS SHOULD PERSIST THRU THURSDAY. MOISTURE
WILL BEGIN TO INCREASE ACROSS THE AREA ON FRIDAY, WITH A CHANCE OF
SHOWERS BY FRIDAY AFTN OVER THE MTNS AND MORE WIDESPREAD SHOWERS
ACROSS THE AREA ON SATURDAY. MTN VALLEY FOG/LOW STRATUS REMAINS
POSSIBLE EACH MORNING.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
JPT/MPR
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