496
FXUS62 KGSP 021031
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
631 AM EDT FRI OCT 2 2026
WHAT HAS CHANGED
AVIATION DISCUSSION UPDATED FOR THE 12Z TAFS.
KEY MESSAGES
1. DRY WITH ABOVE NORMAL TEMPERATURES TODAY. AN ISOLATED
THUNDERSTORM IS POSSIBLE OVER THE SMOKIES THIS EVENING AND
OVERNIGHT.
2. AT LEAST A A MARGINAL RISK OF EXCESSIVE RAIN ON SATURDAY AND
SUNDAY, WHICH COULD LEAD TO INCREASED POTENTIAL FOR LOCALIZED
FLOODING. HOWEVER, SIGNALS ARE MIXED YIELDING LOW CONFIDENCE.
3. COOL AND DRY STARTING TUESDAY, WITH A WARM UP BACK TO NORMAL
BY THE END OF THE WEEK. THERE WILL BE A SMALL CHANCE OF FROST IN
SOME MOUNTAIN LOCATIONS EARLY WEDNESDAY MORNING.
DISCUSSION
KEY MESSAGE 1: DRY WITH ABOVE NORMAL TEMPERATURES TODAY. AN
ISOLATED THUNDERSTORM IS POSSIBLE OVER THE SMOKIES THIS EVENING
AND OVERNIGHT.
ONE LAST SEASONALLY WARM AND DRY DAY IS EXPECTED, COURTESY OF
HIGH PRESSURE AT THE SFC AND ALOFT CENTERED OFF THE COAST OF THE
CAROLINAS. THE RIDGE SHOULD ALLOW FOR TEMPS TO CLIMB A DEGREE OR
TWO WARMER THAN THURSDAY, SO HIGHS IN THE 85 TO 90 DEGREE RANGE
ARE A REASONABLE EXPECTATION. THIS WOULD BE ON THE ORDER OF TEN
DEGREES ABOVE NORMAL, BUT NOWHERE NEAR RECORDS. ALAS, THE UPPER
ANTICYCLONE SHOULD BE ON A WEAKENING TREND BY THE END OF THE DAY AS
IT DRIFTS TO THE SOUTH AND FLATTENS. A FEW SHOWERS OR AN ISOLATED
THUNDERSTORM COULD DEVELOP THIS EVENING OVER SOUTHWEST NC AND THE
SMOKIES, LASTING INTO THE OVERNIGHT HOURS, BUT THE CHANCE OF SEVERE
WEATHER IS VERY LOW.
KEY MESSAGE 2: AT LEAST A A MARGINAL RISK OF EXCESSIVE RAIN ON
SATURDAY AND SUNDAY, WHICH COULD LEAD TO INCREASED POTENTIAL FOR
LOCALIZED FLOODING. HOWEVER, SIGNALS ARE MIXED YIELDING LOW
CONFIDENCE.
BY FRIDAY NIGHT, A SHEARING SHORT WAVE WILL HAVE FLATTENED THE
OLD UPPER RIDGE AND SHOULD BE HELPING TO DRIVE A SFC COLD FRONT
DOWN FROM THE NORTH, BUT STILL NORTH OF THE FCST AREA AT AROUND
DAYBREAK SATURDAY. IT IS THE TIMING AND THE SOUTHWARD PROGRESSION
OF THIS BOUNDARY THAT HAS INJECTED UNCERTAINTY INTO THE WEEKEND
FORECAST. A RELATIVELY WEAK SFC HIGH MOVING FROM THE GREAT LAKES TO
NORTHERN NEW ENGLAND SHOULD ACT TO PUSH THIS BOUNDARY THROUGH AS A
BACK-DOOR COLD FRONT ON SATURDAY, BUT THIS MIGHT NOT HAPPEN UNTIL
LATE IN THE DAY. THE TIMING ON THE AFTERNOON ENSEMBLES IS STILL ALL
OVER THE PLACE, BUT EVENTUALLY THERE IS CONFIDENCE THE BOUNDARY WILL
MOVE SOUTH OF THE FCST AREA BY DAYBREAK SUNDAY, SETTING UP A WEAK
COLD AIR DAMMING WEDGE FOR SUNDAY THAT DRAINS INTO MONDAY. EITHER
WAY, EVENTUALLY PRECIP WILL DEVELOP ACROSS THE FCST AREA AS DEEP
MOISTURE MOVES UP FROM THE SOUTH AND FORCING ARRIVES FROM THE NORTH,
SO HIGH PRECIP PROBS ARE NOT REALLY IN DOUBT. NEITHER ARE THE COOL
TEMPERATURES BY SUNDAY, WITH WIDESPREAD PRECIP AND CLOUD COVER
KEEPING TEMPS ON THE ORDER OF 10 TO 15 DEGREES COOLER THAN NORMAL.
QUITE THE CHANGE IN 48 HOURS OVER THE WEEKEND.
THE MAIN PROBLEM IS THE QPF AND THE POTENTIAL FOR EXCESSIVE
RAINFALL. PATTERN RECOGNITION SUPPORTS THE IDEA THAT WE SHOULD
HAVE AN ELEVATED RISK FOR HEAVY RAIN OVER THE WEEKEND. A WEAKNESS
ALOFT BETWEEN THE BIG MID/UPPER ANTICYCLONE CENTERED OVER THE FOUR
CORNERS REGION AND THE WEAKENING RIDGE OFF THE SOUTHEAST COAST WILL
SUPPORT A MOISTURE PLUME FROM THE GULF AND HIGH PRECIPITABLE WATER
ABOVE 2 INCHES OVER AT LEAST THE SOUTHERN HALF OF THE FORECAST
AREA. HOWEVER, THE PLUME OF STRONG INTEGRATED VAPOR TRANSPORT
CURRENTLY CURLING AROUND TO OUR WEST AND NORTH IS FORECAST TO WEAKEN
CONSIDERABLY BY THE TIME IT MOVES THIS FAR EAST. THE MID/UPPER
FORCING IS ALSO NOT TERRIBLY IMPRESSIVE EITHER, THOUGH LOW LEVEL
FORCING SHOULD BE GOOD ASSUMING WE HAVE A FULL BLOWN WEDGE EAST OF
THE MTNS BY SUNDAY MORNING. THE OFFICIAL FORECAST QPF CREEPS UPWARD
IN MANY SPOTS, WHILE THE MODEL ENSEMBLE QPF CREEPS DOWNWARD SLIGHTLY
IN MANY SPOTS. IN SHORT...MIXED SIGNALS YIELD LOW CONFIDENCE IN
RAINFALL AMOUNTS. IN THIS CASE, THE MARGINAL RISK ON THE EXCESSIVE
RAINFALL OUTLOOKS FOR SATURDAY AND SUNDAY LOOK LIKE A GOOD STARTING
POINT AND ONCE MORE OF THE EVENT IS COVERED BY THE CAMS, THAT WILL
BETTER INFORM THE TREND. IN THE MEAN TIME, WE KEEP AN EYE ON IT.
BY MONDAY MORNING, THE WEDGE SHOULD BE DRAINING AWAY AS THE PARENT
HIGH IS LOST WITH ANOTHER WEAK FRONT COMING DOWN FROM THE NW. THERE
COULD BE SOME SHOWER ACTIVITY OVER THE WEST SIDE OF THE MTNS WITH
THIS FRONT MOVING THRU. TEMPS WILL BE TRICKY, BUT A REBOUND BACK
TO NORMAL IS THE MOST LIKELY OUTCOME.
KEY MESSAGE 3: COOL AND DRY STARTING TUESDAY, WITH A WARM UP BACK
TO NORMAL BY THE END OF THE WEEK. THERE WILL BE A SMALL CHANCE OF
FROST IN SOME MOUNTAIN LOCATIONS EARLY WEDNESDAY MORNING.
THE UPPER LOW MOVING EAST FROM QUEBEC TO THE MARITIME PROVINCES
ON TUESDAY SHOULD DRIVE THE BROAD AXIS OF AN UPPER TROF EAST OF
THE FCST AREA BY TUESDAY, ALLOWING FOR COOL AND DRY HIGH PRESSURE
TO BUILD IN FROM THE UPPER MIDWEST AND GREAT LAKES. THIS AIR MASS
WILL BE SEASONALLY COOL, WITH TEMPS GENERALLY RUNNING AROUND TEN
DEGREES BELOW NORMAL FOR TUESDAY AND WEDNESDAY. THE ONLY MINOR
CONCERN WILL BE LOWS EARLY WEDNESDAY MORNING, WITH 30S COMMON ACROSS
ELEVATIONS ABOVE 3500 FEET. THIS COULD BE COOL ENOUGH TO ALLOW FOR
SOME PATCHY FROST POTENTIAL IN SHELTERED HIGH ELEVATION LOCATIONS,
BUT CONFIDENCE AND LIKELIHOOD ARE LOW. WE STAY UNDER A BROADLY
CYCLONIC FLOW FOR THE REMAINDER OF THE PERIOD, BUT THE AIR MASS
MODIFIES ENOUGH TO GET TEMPS BACK TO NORMAL BY THE END OF THE WEEK.
AVIATION /12Z FRIDAY THROUGH TUESDAY/
AT KCLT AND ELSEWHERE: A RELATIVELY MOIST SW FLOW IS RESULTING
IN AN AREA OF VFR STRATOCU ACROSS UPSTATE SC AND NORTHEAST GA
THIS MORNING...INCLUDING AT KAND. SOME OF THIS COULD BRIEFLY
WAFT OVER KGMU AND KGSP AS WELL, BUT CLOUDS ARE EXPECTED TO
REMAIN AOA 5KFT. OTHERWISE, MOUNTAIN VALLEY FOG/LOW STRATUS IS
CONFINED TO THE NC COUNTIES BORDERING TN. STILL CAN'T RULE OUT
A BRIEF RESTRICTION AT KAVL THIS MORNING, BUT THAT'S LOOKING
INCREASINGLY UNLIKELY. VFR IS THEREFORE FORECAST THROUGH AT LEAST
THIS EVENING, WITH FEW/SCT CUMULUS IN THE 035-050 RANGE EXPECTED
THIS AFTERNOON. CAN'T COMPLETELY RULE OUT A STRAY SHOWER OR PERHAPS
A STORM ACROSS THE MOUNTAINS THIS AFTERNOON, BUT EVEN THIS SMALL
CHANCE WILL MAINLY BE LIMITED TO LOCATIONS WEST OF KAVL. CALM OR
LIGHT/VARIABLE WINDS ARE FORECAST TO BECOME SW AT 5-9 KTS LATE
THIS MORNING THROUGH THE AFTERNOON BEFORE WEAKENING AGAIN THIS
EVENING. INCREASING MOISTURE WILL RESULT IN HIGHER PROBABILITIES
OF RESTRICTIONS LATE TONIGHT/EARLY SATURDAY. FOR NOW, IFR FOG
IS FORECAST AT KAVL PRIOR TO DAYBREAK, WITH MVFR ADVERTISED AT
KHKY. CHANCES FOR RESTRICTIONS ARE LOWER AT THE OTHER TERMINALS,
BUT SCT MVFR LAYERS ARE WARRANTED AT THOSE SITES.
OUTLOOK: WIDESPREAD SHOWERS AND ASSOCIATED RESTRICTIONS DEVELOP
AHEAD OF A COLD FRONT THIS WEEKEND. DRY AND VFR CONDITIONS RETURN
BEHIND THE FRONT EARLY NEXT WEEK.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
JDL/PM
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