173
FXUS62 KGSP 061029
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
629 AM EDT MON OCT 6 2025
SYNOPSIS
HIGH PRESSURE CONTINUES TO CONTROL THE PATTERN THROUGH TUESDAY, WITH
LOW RAIN CHANCES AND A SLOW WARMING TREND. A COLD FRONT ARRIVES
WEDNESDAY, WHICH WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS
ACROSS THE AREA. MUCH DRIER AND COOLER WEATHER IS EXPECTED BEHIND
THE FRONT DURING THE LATTER HALF OF THE WEEK.
NEAR TERM /THROUGH TONIGHT/
AS OF 620 AM EDT MONDAY...
KEY MESSAGES:
1) POCKETS OF MOUNTAIN VALLEY FOG/LOW STRATUS THIS MORNING WITH
PATCHY FOG POSSIBLE ACROSS MUCH OF THE AREA TUESDAY MORNING
2) SCATTERED SHOWERS RETURN TODAY, MAINLY ALONG AND WEST OF I-26
3) ABOVE NORMAL TEMPERATURES CONTINUE
4) UPSLOPE SHOWERS MAY DEVELOP ALONG THE ESCARPMENT THIS EVENING
INTO TONIGHT
SOME POCKETS OF MOUNTAIN VALLEY FOG AND LOW STRATUS DEVELOPED
OVERNIGHT, MAINLY ACROSS PORTIONS OF THE LITTLE TN VALLEY, DESPITE
CLOUD COVER. SOME PATCHY FOG IS ALSO NOTED AT KHKY THIS MORNING. FOG
AND LOW STRATUS SHOULD LIFT SHORTLY AFTER SUNRISE. TEMPS THIS
MORNING ARE MOSTLY RANGING FROM THE MID 50S TO MID 60S THANKS TO
INCREASING STRATOCU OVERNIGHT.
OTHERWISE, UPPER ANTICYCLONE REMAINS OVER EASTERN UNITED STATES
TODAY BEFORE IT GETS SHUNTED OVER THE SOUTHEAST THIS EVENING INTO
TONIGHT IN RESPONSE TO AN UPPER TROUGH PUSHING ACROSS THE UPPER
MIDWEST AND GREAT LAKES REGION. MEANWHILE, THE SW PERIPHERY OF A SFC
HIGH (CENTERED OVER THE WESTERN ATLANTIC) WILL REMAIN EXTENDED OVER
THE SOUTHEAST AS A COLD FRONT APPROACHES OUT OF THE CENTRAL UNITED
STATES. THIS WILL HELP KEEP THE INFLUX OF ATLANTIC MOISTURE AROUND
THROUGH THE PERIOD. DRY CONDITIONS WILL LINGER THROUGH DAYBREAK
BEFORE RAIN CHANCES RETURN LATER THIS MORNING. AREAS ALONG AND WEST
OF I-26 WILL ONCE AGAIN HAVE THE BEST POTENTIAL TO SEE SCATTERED
SHOWERS TODAY SO THE HIGHEST POPS (25% TO 35%) ARE IN PLACE ACROSS
THESE ZONES. HIGHS WILL BE SIMILAR TO YESTERDAY, ENDING UP A FEW
DEGREES ABOVE NORMAL ACROSS THE WESTERN ZONES AND AROUND 5 DEGREES
ABOVE NORMAL ACROSS THE EASTERN ZONES. WITH E/SE FLOW STICKING
AROUND ACROSS THE MOUNTAINS THIS EVENING INTO LATE TONIGHT, LIGHT
RAIN AND/OR DRIZZLE COULD DEVELOP ALONG THE ESCARPMENT. THUS,
MAINTAINED SLIGHT CHANCE POPS (15% TO 20%) FOR AREAS ALONG/NEAR THE
ESCARPMENT. GUIDANCE HAS BEEN CONSISTENT REGARDING PATCHY FOG
DEVELOPING ACROSS MUCH OF THE FORECAST AREA OVERNIGHT INTO DAYBREAK
TUESDAY. LOWS TUESDAY MORNING WILL END UP A FEW DEGREES WARMER
COMPARED TO THIS MORNING, ENDING UP ~10-15 DEGREES ABOVE NORMAL.
SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
AS OF 133 AM EDT MONDAY: AREA OF HIGH PRESSURE THAT HAS CONTROLLED
THE SYNOPTIC PATTERN OF OUR AREA FOR THE PAST FEW DAYS AND WILL
SHIFT FURTHER OFFSHORE, WHILE LOSING ITS GRIP ON THE CWFA BY
TUESDAY. IN TURN, A DIGGING UPPER TROUGH WILL BE IN THE PROCESS OF
MOVING INTO THE EASTERN CONUS WITH AN ASSOCIATED COLD FRONT. WEAK
SOUTHERLY LOW-LEVEL WAA WILL FILTER IN BEGINNING TUESDAY AND HELP TO
SCATTER ANY RESIDUAL WEDGE WITH DEEPER DAYTIME MIXING. SOME MODELS
TRY TO DEVELOP PEAK HEATING WAA SHOWERS, BUT CONFIDENCE ISN'T HIGH
ENOUGH FOR A MENTIONABLE POP AT THIS TIME. EXPECT AFTERNOON HIGHS TO
RUN A CATEGORY OR SO ABOVE ON TUESDAY.
CHANGES REALLY TAKE PLACE TUESDAY NIGHT INTO WEDNESDAY AS
THE AFOREMENTIONED COLD FRONT ENCROACHES THE CWFA FROM THE
NORTHWEST. MODEL GUIDANCE SHOW SOME QPF RESPONSE STARTING AS EARLY
AS OVERNIGHT TUESDAY NEAR THE NC/TN BORDER. STILL SOME DISCREPANCIES
AMONGST MODEL GUIDANCE AS FAR AS TIMING, BUT AN INTERESTING TREND
IS THE AMOUNT OF SBCAPE DETERMINISTIC GUIDANCE PRODUCE AHEAD
OF THE FRONT, WITH SOME INDICATING OVER 1000 J/KG. THE AMOUNT
OF DESTABILIZATION WILL DEPEND ON THE TIMING OF THE FRONT MOVING
ACROSS THE AREA. A FASTER SOLUTION WOULD RESULT IN LESS INSTABILITY
AND DEEP LAYER SHEAR, AND WOULD PRODUCE AT MOST, LOOSELY ORGANIZED
CONVECTION DURING THE FIRST OF WEDNESDAY. A SLOWER SOLUTION WILL
ALLOW FOR BETTER DESTABILIZATION AND AN UPTICK IN DEEP LAYER
SHEAR (25-35 KTS), BRINGING IN THE BETTER QPF RESPONSE DURING
PEAK HEATING. THE BETTER FORCING WILL BE JUST TO THE NORTH, BUT
MODEL GUIDANCE CONTINUE TO HINT AT BETTER ORGANIZED CONVECTION IN
THE NORTH CAROLINA FOOTHILLS AND WESTERN PIEDMONT WHERE SHEAR IS
HIGHER. THIS LIKELY MAKES THE SEVERE THREAT NONZERO, BUT CONFIDENCE
IS STILL ON THE LOWER SIDE UNTIL WE RECEIVE MORE HIGH RESOLUTION
DATA. ANOTHER AREA OF POSSIBLE CONCERN WOULD BE ALONG AND SOUTHEAST
OF THE I-85 CORRIDOR, WHERE DEEP LAYER SHEAR MAY NOT BE AS HIGH,
BUT PROBABILITY FOR HIGHER SBCAPE BASED ON THE SREF AND OTHER GLOBAL
ENSEMBLES IS EVIDENT, WHICH COULD ALLOW FOR DEEPER CONVECTION TO
DEVELOP. WILL NEED TO CONTINUE TO MONITOR THE THREAT, BUT NOTHING
GROUNDBREAKING AT THIS TIME. DEEP WARM CLOUD LAYER (FREEZING LEVEL:
~12,000') WITH PWAT VALUES AROUND 1.50" LIKELY WILL RESULT IN AREAS
OF HEAVIER RAINFALL RATES WITH ANY SHOWERS OR THUNDERSTORMS, BUT
HYDRO THREAT IS VERY LOW DUE TO THE FASTER STORM MOTION AND DRY
ANTECEDENT CONDITIONS. AFTERNOON HIGHS ON WEDNESDAY WILL BE 5-10
DEGREES ABOVE NORMAL AS BETTER COMPRESSIONAL WARMING WILL BE IN
STORE AHEAD OF THE FRONT. THERE IS GOOD CONSENSUS ON A FULL FROPA
OCCURRING LATER IN THE DAY WEDNESDAY INTO WEDNESDAY NIGHT. VERY
GOOD DRY AIR ENTRAINMENT AND COOLER AIR IS EXPECTED BEHIND THE
FRONT WEDNESDAY NIGHT, WHICH SHOULD HELP OVERNIGHT LOWS DIP A
CATEGORY OR SO LOWER COMPARED TO TUESDAY NIGHT.
LONG TERM /THURSDAY THROUGH SUNDAY/
AS OF 152 AM EDT MONDAY: A STOUT CONTINENTAL SURFACE HIGH WILL
SHIFT FROM THE GREAT LAKES REGION INTO THE NORTHEASTERN CONUS
THURSDAY INTO THURSDAY NIGHT. LOW-LEVEL NORTHEASTERLY CAA WILL
HELP TEMPERATURES TO DIP ~10 DEGREES BELOW NORMAL FOR AFTERNOON
HIGHS ON THURSDAY AND FRIDAY AS THE SURFACE HIGH NOSES INTO THE
REGION IN WEDGE-LIKE FASHION. LOW-AMPLITUDE TROUGH SEEMS TO GET
CARVED OUT OVER THE SOUTHEASTERN CONUS BY FRIDAY AS AN UPPER
ANTICYCLONE DEEPENS OVER THE SOUTHERN HIGH PLAINS AND NORTHERN
MEXICO. WITH THE SHORT-TERM FRONT BECOMING STALLED ALONG THE
GULF AND SOUTHEAST COAST, ENOUGH FORCING SHOULD INDUCE SURFACE
CYCLOGENESIS ALONG THE BOUNDARY OVER THE GULF STREAM AND HELP TO
POTENTIALLY DEVELOP A COASTAL LOW RIGHT OFF THE SOUTHEAST COAST
BY THE UPCOMING WEEKEND. STILL COME DISCREPANCIES ON THE EXACT
PLACEMENT OF DEVELOPMENT AND TIMING, BUT THERE SEEMS TO BE MORE
AGREEMENT WITH THIS SCENARIO AS THIS ALSO HELPS TO BREAKDOWN THE
AFOREMENTIONED SURFACE HIGH AND SHIFT THE CENTER OFFSHORE THE
NEW ENGLAND COAST. EITHER WAY, THE CWFA LOOKS TO REMAIN MOSTLY DRY
THROUGH A GOOD PORTION OF THE EXTENDED PERIOD AS ANY IMPACTS OF A
COASTAL LOW WOULD REMAIN EAST OF THE CWFA, BUT CHANGES WILL OCCUR
AND THE FORECAST SHOULD BE MONITORED THROUGHOUT THE WEEK LEADING
UP TO THIS POTENTIAL SETUP OVER THE UPCOMING WEEKEND. TEMPERATURES
SEEM TO TAKE ON A GRADUAL REBOUND AFTER FRIDAY AS THE AIRMASS
SLOWLY MODIFIES.
AVIATION /12Z MONDAY THROUGH FRIDAY/
AT KCLT AND ELSEWHERE: STRATOCU IS IN PLACE ACROSS MOST OF THE
TERMINALS AS OF 10Z AND STRATOCU WILL CONTINUE TO EXPAND IN COVERAGE
THROUGH DAYBREAK. SOME MOUNTAIN VALLEY FOG AND LOW STRATUS MANAGED
TO DEVELOP OVERNIGHT DESPITE THE CLOUD COVER. ALTHOUGH FOG AND LOW
STRATUS ARE NOT IMPACTING KAVL AS OF 10Z, THEY BOTH WILL REMAIN
POSSIBLE THROUGH DAYBREAK IF ANY BREAKS IN THE CLOUDS OCCUR. KHKY IS
REPORTING MVFR CIGS AS OF 10Z. CIGS WILL GRADUALLY LOWER TO MVFR
LEVELS ACROSS THE SC UPSTATE TERMINALS AND AT KAVL AROUND OR SHORTLY
AFTER SUNRISE. CIGS WILL LIFT BACK TO VFR LEVELS BY EARLY AFTERNOON.
DRY CONDITIONS LINGER THROUGH THE MORNING HOURS BEFORE RAIN CHANCES
RETURN ACROSS THE SC UPSTATE THIS AFTERNOON AND EARLY EVENING.
MAINTAINED PROB30S FOR -SHRA ACROSS THE SC TERMINALS. WINDS WILL
REMAIN SE AT KAVL THROUGH THE PERIOD. WINDS EAST OF THE MOUNTAINS
WILL GENERALLY BE NE/ENE ALTHOUGH KCLT AND KHKY SHOULD SEE WINDS
TURN MORE E/ESE THIS AFTERNOON AND EVENING. WIND SPEEDS WILL ONCE
AGAIN RANGE FROM ~5-10 KTS TODAY. CIGS WILL GRADUALLY LOWER
OVERNIGHT INTO DAYBREAK TUESDAY BECOMING MOSTLY MVFR, ALTHOUGH KAVL
COULD SEE IFR TO LIFR CIGS DEVELOP. GUIDANCE CONTINUES TO BE
CONSISTENT REGARDING THE PATCHY FOG POTENTIAL ACROSS THE TERMINALS
EARLY TUESDAY MORNING, WITH THE EXCEPTION OF KCLT WHICH MAY SEE VFR
VSBYS CONTINUE.
OUTLOOK: SHOULD SEE DRIER CONDITIONS ON TUESDAY WITH RESTRICTIONS
LIFTING BY TUESDAY AFTERNOON. A COLD FRONT WILL BRING RAIN CHANCES,
AS WELL AS RESTRICTIONS, TUESDAY NIGHT INTO WEDNESDAY NIGHT BEFORE
DRIER CONDITIONS RETURN THURSDAY INTO FRIDAY.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...CAC
NEAR TERM...AR
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...AR
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