282
FXUS62 KGSP 101053
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
653 AM EDT SAT OCT 10 2026
WHAT HAS CHANGED
UPDATED AVIATION DISCUSSION FOR THE 12Z TAFS.
KEY MESSAGES
1. ISAIAS IS EXPECTED TO TRACK NORTHWARD TODAY, INCREASING
THE THREATS FOR FLOODING, LANDSLIDES OVER EASTERN PARTS OF THE
MOUNTAINS, STRONG WIND GUSTS, AND ISOLATED SEVERE STORMS ALONG
AND SOUTH/EAST OF I-85 THROUGH TONIGHT. THE RISKS SHOULD PEAK
BETWEEN LATE AFTERNOON AND THE EARLY MORNING HOURS ON SUNDAY.
2. GUSTY NORTHWEST WINDS MAY DEVELOP ACROSS THE HIGHER ELEVATIONS
SUNDAY NIGHT THROUGH MONDAY AFTER THE REMNANT CIRCULATION OF ISAIAS
PASSES TO THE NORTH. AFTER THAT, DRY WEATHER WITH A WARMING TREND
INTO THE MIDDLE OF NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: ISAIAS IS EXPECTED TO TRACK NORTHWARD TODAY, INCREASING
THE THREATS FOR FLOODING, LANDSLIDES OVER EASTERN PARTS OF THE
MOUNTAINS, STRONG WIND GUSTS, AND ISOLATED SEVERE STORMS ALONG AND
SOUTH/EAST OF I-85 THROUGH TONIGHT. THE RISKS SHOULD PEAK BETWEEN
LATE AFTERNOON AND THE EARLY MORNING HOURS ON SUNDAY.
POST-TROPICAL CYCLONE ISAIAS SHOULD TRACK NORTHWARD AND WEAKEN
TODAY ACROSS MAINLY AL, AND THEN ACROSS MIDDLE TN TONIGHT, RAISING
SEVERAL WEATHER RISKS ACROSS THE FORECAST AREA. THE STORM APPEARS
TO BE MOVING INLAND A LITTLE FASTER THAN PREVIOUSLY THOUGHT,
SO THE TIMING OF PRECIP ARRIVAL WAS MOVED UP YET AGAIN. COULD
THIS BE AN INDICATOR FOR THREATS INCREASING EARLIER? ANY RECENT
TRACK CHANGES HAVE MINIMAL IMPACT ON THE FORECAST. WE'RE STILL
EXPECTING PRECIP PROBS TO RAMP UP THROUGH DAYBREAK, FOLLOWED BY
INCREASING RAINFALL RATES AS WE GET THROUGH THE MIDDLE PART OF THE
DAY, WITH THE HIGHEST RISK PEAKING BETWEEN LATE AFTERNOON AND THE
EARLY MORNING HOURS ON SUNDAY. SOME OF THE DETAILS REMAIN ELUSIVE.
THE QPF CONTINUES TO UNDERGO ADJUSTMENTS FROM ONE RUN TO THE NEXT,
BUT IN GENERAL CONTINUES TO FAVOR VERY HIGH AMOUNTS IN THE SOUTHEAST
UPSLOPE FLOW LOCATIONS NEAR THE BLUE RIDGE ESCARPMENT. HIGHEST
VALUES HAVE COME DOWN BY ABOUT AN INCH, BUT THAT ISN'T ENOUGH
TO SUBSTANTIALLY CHANGE THE FCST OVER THE MTNS. WHAT IS MORE
INTERESTING IS THE SUGGESTION OF A BAND OF NORTHWARD-TRAINING
SHOWERS AND STORMS WILL TRANSLATE SLOWLY EAST ACROSS THE FCST AREA
LATE THIS AFTERNOON AND THIS EVENING AS ISAIAS MAKES THE GRADUAL
TRANSITION TO EXTRATROPICAL. TAKING THIS INTO ACCOUNT WITH HIGHER
PRECIP AMOUNTS FARTHER EAST ACROSS UPSTATE SC, THE FLOOD WATCH
WILL BE EXPANDED TO INCLUDE THE I-26 CORRIDOR. THIS LINES UP BEST
WITH THE UPDATED WATCH FROM THE CAE OFFICE. THE QPF DOESN'T REALLY
SUPPORT EXPANSION ANY FARTHER EAST THAN SPARTANBURG AND LAURENS
COUNTIES AT THIS TIME. THIS TREND ALSO SUGGESTS MAYBE A GREATER
RISK OF LANDSLIDES NEAR THE ESCARPMENT OVER NC AND THE BLACK MTNS,
AND MAYBE A DECREASING TREND OVER THE BALSAMS AND THE ESCARPMENT
NEAR THE SC/NC BORDER. STILL A LARGE AREA OF POTENTIAL 5-8 INCH
STORM TOTAL RAINFALL IN THOSE LOCATIONS. THE RAIN SHOULD LIFT OUT TO
THE EAST DURING THE OVERNIGHT/EARLY MORNING HOURS SUNDAY. I WOULD
LIKE TO SAY THAT CONFIDENCE IS BETTER, BUT THERE ARE CONCERNING
DIFFERENCES BETWEEN THE GLOBAL MODELS AND THE CAMS, SO FAILURE MODES
ABOUND, PARTICULARLY WHERE THE COLD AIR DAMMING WEDGE IS CONCERNED.
LITTLE CHANGE WAS MADE TO THE WIND HAZARDS, THOUGH INCORPORATING
SOME OF THE HIGHER-END OF THE NBM SUGGESTS MOST PLACES EAST OF
THE MTNS HAVE SIMILAR CHANCES OF SEEING PERIODS OF STRONGER WIND
GUSTS ON THE ORDER OF 30-40 MPH THROUGH THIS EVENING. THE MAIN
CONCERN IS SATURATED GROUND AS RAIN ACCUMULATES, MAKING IT EASIER
FOR THE GUSTY WINDS TO KNOCK DOWN AND UPROOT SOME TREES. FOR NOW,
THAT WOULD SEEM TO PRECLUDE THE EASTERN UPSTATE AND I-77 CORRIDOR
FROM CONSIDERATION, BUT WE WILL MONITOR FOR EXPANSION IF THE HIGHER
PRECIP AMOUNTS SHIFT EASTWARD. ELEVATIONS ABOVE 3500 FEET WILL
HAVE THE BEST SHOT AT SEEING WIND GUSTS THAT ACTUALLY MEET CRITERIA.
AS FOR THE SEVERE STORM RISK, THAT IS MORE CONDITIONAL ON THE
SCOURING OF THE COLD AIR DAMMING WEDGE EAST OF THE MTNS. THE
WEDGE APPEARS LIKELY TO HOLD THROUGH THE BETTER PART OF THE DAY,
MEANING OUR RISK WOULD BE VERY LOW UNTIL AFTER SUNSET. AFTER 00Z,
THE CENTER OF ISAIAS REMNANTS WOULD BE MOVING PAST TO OUR WEST
AND THE BEST SOUTHERLY FLOW AT LOW LEVELS WOULD ATTEMPT TO SCOUR
THE WEDGE AND MOVE THE BOUNDARY NORTHWARD. THE 03Z RAP DOES THAT,
UNCOVERING THE NORTHEAST GA AND UPSTATE SC ZONES THROUGH THE
PRE-DAWN HOURS SUNDAY WITH SFC-BASED CAPE REACHING 500 J/KG AND
EFFECTIVE SHEAR REACHING 40 KT. IN OTHER WORDS, ENOUGH BUOYANCY
AND SHEAR TO PUT US IN THE ROTATING STORM BUSINESS. THE 00Z HREF
DOES JUST THAT, WITH JOINT PROBS REACHING 40-50% OVERNIGHT ALONG
AND SOUTH OF I-85 AND WEST OF I-77. THAT RAISES OUR CONCERNS FOR
ISOLATED BRIEF TORNADOES IN ANY LOW-TOPPED STORMS WITH SUPERCELL
CHARACTERISTICS. THIS THREAT WOULD SHIFT EASTWARD ACROSS METRO
CHARLOTTE SUNDAY MORNING AFTER SUNRISE.
THE THREATS SHOULD COME TO AN END BY THE MIDDLE PART OF THE DAY
ON SUNDAY.
KEY MESSAGE 2: GUSTY NORTHWEST WINDS MAY DEVELOP ACROSS THE HIGHER
ELEVATIONS SUNDAY NIGHT THROUGH MONDAY AFTER THE REMNANT CIRCULATION
OF ISAIAS PASSES TO THE NORTH. AFTER THAT, DRY WEATHER WITH A
WARMING TREND INTO THE MIDDLE OF NEXT WEEK.
ONCE THE REMNANTS OF ISAIAS HAVE MOVED PAST TO THE NORTH SUNDAY
EVENING, THE WIND SHOULD VEER AROUND TO THE NW AND BECOME GUSTY
ACROSS THE HIGHER TERRAIN OWING TO A LINGERING STRONG PRESSURE
GRADIENT ON THE BACK SIDE OF THE SYSTEM. MOISTURE ON THE BACK SIDE
WILL GET FORCED UP AS WELL, SO A SMALL PRECIP CHANCE WILL BE KEPT
THROUGH MONDAY MORNING. AFTER THAT, CUE THE WARMUP AS AN UPPER
RIDGE BUILDS IN FROM THE WEST. TEMPS ARE ALREADY EXPECTED TO BE
ABOVE NORMAL ON MONDAY, BUT MAKE IT TO TEN DEGREES ABOVE NORMAL
BY THE MIDDLE OF NEXT WEEK. CONFIDENCE GOES DOWN AFTER THAT. THE
NBM STARTS TO DROP TEMPS BACK DOWN TOWARD NORMAL TOWARD THE END
OF THE WEEK, BUT SEVERAL OF THE MODEL SOLUTIONS STILL HAVE US
UNDER THE RIDGE ASSOCIATED WITH AN UPPER ANTICYCLONE TRAVERSING
THE SOUTHEAST. BIG CHANGES COULD BE IN STORE FOR NEXT WEEKEND IF
THE COOL GFS/CANADIAN WORK OUT.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
AT KCLT AND ELSEWHERE: SHRA BECOMING WIDESPREAD WITH GUSTY WINDS AND
MVFR RESTRICTIONS SLOWLY DEVELOPING. EXPECT CONDITIONS TO
DETERIORATE THROUGH THE MORNING WITH IFR CIGS AND MVFR TO IFR VSBY.
LIFR CIGS POSSIBLE. CAN'T RULE OUT A TS THIS MORNING, BUT CHANCES
ARE BETTER DURING THE AFTERNOON AND EVENING. IFR VSBY AND CIGS
EXPECTED DURING THE AFTERNOON AS WELL. VSBY GOES BACK TO MVFR FOR
THE EVENING WITH IFR TO LIFR CIGS, ALONG WITH LOWER CONDITIONS IN
ANY HEAVIER SHOWERS OR TS. NE WINDS BECOME GUSTY THROUGH THE MORNING
WITH STRONGER WINDS AND GUSTS DURING THE DAY, GENERALLY AROUND 30
KTS BUT COULD BE HIGHER. KAVL MAY SEE WINDS FLIP/FLOP UP THEN DOWN
VALLEY WITH AN EASTERLY LOW LEVEL JET NEAR THE RIDGE TOPS. MORE
SUSTAINED SE WIND WITH LOW END GUSTS EXPECTED FOR THE AFTERNOON INTO
THE EVENING. EXPECT LLWS TO DEVELOP AT KAVL GIVEN THE AFORE
MENTIONED LOW LEVEL JET. KHKY WILL SEE LLWS IN THE AFTERNOON.
CHANCES ARE LOWER ELSEWHERE, BUT MAY STILL DEVELOP.
OUTLOOK: CONVECTION AND RESTRICTIONS MOVE EAST OF THE AREA BY SUNDAY
AFTERNOON. WINDS TURN SW AND GUSTY FOR ALL BUT KAVL WHERE NW GUSTY
WINDS DEVELOP. SUNDAY MORNING. LOCALLY STRONGER OR DAMAGING WINDS
ASSOCIATED WITH +SHRA OR TSRA CANNOT BE RULED OUT SATURDAY NIGHT.
GUSTY NE WINDS--SE AT KAVL--ARE EXPECTED THROUGH SAT NIGHT WITH
LIGHTER, BUT STILL GUSTY SW WIND ON SUNDAY. VFR WITH GUSTY NW WIND
ON MONDAY. VFR OUTSIDE OF MOUNTAIN VALLEY FOG TUESDAY AND WEDNESDAY,
WITH LIGHT WINDS.
GSP WATCHES/WARNINGS/ADVISORIES
GA...WIND ADVISORY UNTIL 8 AM EDT SUNDAY FOR GAZ010-017-018-026-028-
029.
FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR GAZ010-017-018-026-
028-029.
NC...WIND ADVISORY UNTIL 8 AM EDT SUNDAY FOR NCZ033-048>053-058-059-
062>065-501-503-505-507-509.
FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR NCZ033-049-050-052-
053-059-062>065-501>510.
HIGH WIND WARNING UNTIL 8 AM EDT SUNDAY FOR NCZ048>053-058-059-
062>064.
SC...WIND ADVISORY UNTIL 8 AM EDT SUNDAY FOR SCZ010-011-019-101>107.
FLOOD WATCH THROUGH SUNDAY AFTERNOON FOR SCZ010>012-019-
101>109.
PM/RWH
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