788
FXUS62 KGSP 030003
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
803 PM EDT SAT AUG 2 2025
SYNOPSIS
COLD AIR DAMMING SETUP WILL KEEP TEMPERATURES WELL BELOW NORMAL
THROUGH THE EARLY PART OF THE NEXT WEEK. A GRADUAL WARMING TREND IS
EXPECTED BY THE MIDDLE PART OF NEXT WEEK INTO THE WEEKEND. SHOWER
AND THUNDERSTORM CHANCES STICK AROUND EACH DAY THROUGH NEXT WEEK,
WITH THE BEST CHANCES LIKELY AFTER MONDAY.
NEAR TERM /THROUGH SUNDAY/
AS OF 745 PM EDT SATURDAY: THE SYNOPTIC SCALE FEATURE OF INTEREST
THIS WEEKEND REMAINS THE UNCOMMON SUMMER CAD REGIME. AREAS OF
DRIZZLE ARE NOTED ON BASE REFLECTIVITY AND ON SFC OBS HERE AND
THERE AROUND THE CWA AT THIS TIME. SCATTERED SHOWERS CONTINUE
NEAR THE WEDGE BOUNDARY OVER THE MOUNTAINS AND FOOTHILLS. WHILE
THESE ARE WEAKENING DIURNALLY, SOME CHANCE WILL CONTINUE IN THOSE
AREAS OVERNIGHT AND ELEVATED CELLS MAY REDEVELOP OVERNIGHT WITH LLJ
DEVELOPING OVER WEDGE. DRY NE FLOW IS BEGINNING TO LIFT CLOUD BASES
IN THE NC PIEDMONT, AND THIS SHOULD EXPAND WESTWARD AND REDUCE THE
COVERAGE OF DRIZZLE OVER THE NEXT FEW HOURS. FOG APPEARS LIKELY TO
DEVELOP WHERE PERSISTENT PRECIP OCCURS AND SFC SATURATION PERSISTS,
CURRENTLY MOST LIKELY ACROSS THE MOUNTAINS.
DESPITE THE LINGERING COOL AIR WEDGE AND NE SFC FLOW ON SUNDAY,
CONTINUED IMPINGEMENT OF DRIER AIR FROM THE NNE WILL GIVE RISE
TO INCREASING CHANCES OF BRIGHTENING SKIES ALONG AND EAST OF I-
77 BUT MORE A PESSIMISTIC SKY AND SHOWER FCST EXISTS THE FURTHER
SOUTH ONE TRAVELS ALONG THE APPALACHIAN CHAIN. SHOWERS SHOULD
BECOME NUMEROUS AGAIN ON SUNDAY ACROSS THE SW CWA AND MUCH OF THE
MOUNTAINS AND FOOTHILLS WILL SEE 70S ONCE AGAIN FOR MAXES.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
AS OF 100 PM EDT SATURDAY: IN-SITU CAD WILL BE STEADILY LOCKED
IN OVER THE AREA TO START THE FORECAST PERIOD AS A SURFACE HIGH
LOCATED OFFSHORE THE NEW ENGLAND COAST CONTINUES TO NOSE IN FROM
THE NORTHEAST. DRY SURFACE LAYER AND WEAK ATLANTIC FETCH ATOP THE
SURFACE WILL HOLD THE CAD DOME STRONG, ESPECIALLY WITH A LI BETWEEN
4-6 PER THE SREF KEEPING HIGH STATIC STABILITY IN PLACE. IN THIS
CASE, CAD SHOULD STICK AROUND THROUGH THE SHORT-TERM PERIOD WITHOUT
AN OBVIOUS EROSION MECHANISM. MODEL GUIDANCE HAVE BEEN PERSISTENT
OVER THE PAST 24-36 HOURS OF DRIER CONDITIONS FOR MONDAY AS A
SECOND SURFACE HIGH SHIFTS OVER NEW ENGLAND AND ATLANTIC CANADA
AND REINFORCES THE CAD DOME AND DRIER AIR AT THE SURFACE. POPS
ONLY REMAIN IN THE SLIGHT CHANCE TO CHANCE RANGE IN THIS SETUP AS
LIGHT ON AND OFF DRIZZLE AND SHOWERS STILL CAN'T BE RULED OUT IN
THE PRESENCE OF CAD. HOWEVER, A SLUG OF BETTER DEEP LAYER MOISTURE
WILL RETURN MONDAY NIGHT INTO TUESDAY AS A DIGGING SHORTWAVE TROUGH
MARCHES EAST FROM THE CENTRAL CONUS, TOGGLING THE FLOW ABOVE THE
SURFACE LAYER TO A SOUTH-SOUTHWESTERLY COMPONENT. AS A RESULT,
AN UPTICK IN POPS IS EVIDENT, ESPECIALLY BY TUESDAY WITH THE
RETURN OF BETTER MOISTURE AND ISENTROPIC LIFT. INSTABILITY WILL
BE VERY LOW, BUT THERE IS EVIDENCE OF ELEVATED INSTABILITY, WHICH
COULD RESULT IN HEAVIER SHOWERS AND ISOLATED THUNDER DURING THE
DIURNAL PERIOD TUESDAY. POPS RAMP BACK UP INTO THE LIKELY CATEGORY,
ESPECIALLY IN THE SOUTHWEST MOUNTAINS AND LOCATIONS WEST OF I-26,
WHERE THE BETTER ISENTROPIC FORCING IS LOCATED.
THE DRIEST AIR WILL BE PRESENT SUNDAY NIGHT AND MONDAY, LEADING
DEWPOINTS TO DROP INTO THE UPPER 50S TO LOWER 60S. IN COMBINATION
WITH THE COOLER, DRIER SUBCLOUD LAYER AND EXTENSIVE CLOUD COVER
SETTLED IN SUNDAY NIGHT, EXPECT OVERNIGHT VALUES TO END UP 4-8
DEGREES BELOW NORMAL. CONTINUED CAD CONDITIONS WILL KEEP AFTERNOON
HIGHS ON MONDAY 10-15 DEGREES BELOW NORMAL. SLIGHTLY BETTER MOISTURE
TRANSPORT WILL HELP TO UPTICK DEWPOINTS A FEW DEGREES BY MONDAY
NIGHT TO GO ALONG WITH CONTINUED CLOUD COVER. OVERNIGHT LOWS WILL
RUN 3-6 DEGREES BELOW NORMAL AS A RESULT. WITH BETTER WAA FILTERING
IN ABOVE THE CAD DOME, HELPING TO RAISE DEWPOINTS, TEMPERATURES
ARE FORECASTED TO UPTICK A FEW DEGREES AND ONLY RUN 8-12 DEGREES
BELOW NORMAL.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
AS OF 145 PM EDT SATURDAY: THE AFOREMENTIONED SHORTWAVE TROUGH IN
THE SHORT TERM IS SHOWN SHIFTING OVER THE DEEP SOUTH AND BREAKING
DOWN AS THE FEATURE GETS MUSHED IN BETWEEN AN ANTICYCLONE OVER
THE SOUTHWESTERN CONUS AND ANOTHER OVER THE WESTERN ATLANTIC
WEDNESDAY AND THURSDAY. IN RESPONSE, DEEP MOISTURE WILL CONTINUE
TO TRANSLATE OVER THE SOUTHEASTERN CONUS THROUGH A GOOD PORTION
OF THE WORKWEEK. THE MIDDLE PART OF THE WEEK WILL KEEP A WEAK
IN-SITU CAD IN PLACE, BUT THE STALLED BOUNDARY TO THE SOUTH WILL
HAVE A SURFACE LOW RIDE ALONG IT AND POTENTIALLY DEEPEN OFFSHORE
THE CAROLINA COAST ONCE IT TAPS INTO THE GULF STREAM. IN THIS CASE,
THE CAD DOME SHOULD BEGIN TO GRADUALLY ERODE BY NEXT THURSDAY AND
FRIDAY PER THE GFS AND CANADIAN FROM THE COASTAL LOW, LEADING
TO BETTER SURFACE DIVERGENCE. THE ECMWF ISN'T AS EXCITED ABOUT
THE COASTAL LOW POTENTIAL, BUT ALL OF THE DETERMINISTIC FILTER IN
A STRONG ATLANTIC FETCH IN THE PRESENCE OF THE STALLED BOUNDARY
THROUGH MUCH OF THE WORKWEEK. EXPECT HIGHER PWAT VALUES (~2.00")
AND FOR THE OVERALL SETUP TO BE UNSETTLED THROUGH A GOOD PORTION OF
THE FORECAST PERIOD, WITH DIURNAL ENHANCEMENT. BETTER SOLAR HEATING
WILL LIKELY ERODE ANY TRUE CAD BY THE END OF THE WORKWEEK AS ONLY A
RESIDUAL COLD POOL POSSIBLY HOLDS STEADY. TEMPERATURES FOR WEDNESDAY
REMAIN 5-10 DEGREES BELOW NORMAL, BUT A GRADUAL WARMING TREND IS
EVIDENT THROUGH THE REST OF THE FORECAST PERIOD, BUT VALUES SHOULD
STAY A FEW TICKS OR SO BELOW NORMAL AS ELEVATED POPS AND CLOUD COVER
HOLD STEADY WITH THE PRESENCE OF A WEAK RESIDUAL COLD POOL.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
AT KCLT AND ELSEWHERE: NE WINDS AT ALL SITES THIS PERIOD EXCEPT
KAVL (WHICH REMAINS SE'LY) OWING TO SFC HIGH PRESSURE RIDGING DOWN
THE EAST COAST IN COLD-AIR DAMMING CONFIGURATION. THIS FLOW IS
BRINGING DRIER LOW-LEVEL AIR SUCH THAT CIGS ARE EXPECTED TO TREND
GRADUALLY HIGHER TONIGHT FROM EAST TO WEST ACROSS THE TERMINAL
AREA. CLOUD BASES ARE STARTING OFF MOSTLY MVFR BUT AREAS OF -DZ
ARE ASSOCIATED WITH PERIODS OF IFR VSBY/CIG. THE DZ MAY COME AND
GO AND TEMPOS REFLECT THE VARIABLE CONDITIONS. DZ SHOULD DIMINISH
WITH THE ARRIVAL OF THE DRIER AIR. A FEW TRUE -SHRA MAY CONTINUE
OVER THE MOUNTAINS/FOOTHILLS NEAR KAVL/KHKY/KAND THIS EVENING BUT
IN LIGHT OF THE RESTRICTIONS THOSE ARE ONLY MENTIONED AS VCSH. KAVL
AND KAND STAND THE BEST CHANCE OF PRECIP AFTER MIDNIGHT, WITH KAND
GETTING PROB30 FOR SHRA AND KAVL SEEING IFR REDEVELOP. ALTHOUGH
CIGS LIFT TO VFR BY MIDDAY SUNDAY, CHANCE OF ELEVATED SHRA OR TSRA
WARRANTS PROB30S AT THE MORE WESTERN SITES.
OUTLOOK: RELATIVELY COOL AND DAMP CONDITIONS ARE EXPECTED TO
CONTINUE MONDAY. ALTHOUGH TEMPERATURES ONLY GRADUALLY WARM BACK
UP OVER THE REMAINDER OF THE WEEK, PRECIPITATION CHANCES TREND
TOWARD A MORE TYPICAL SUMMERTIME REGIME WITH CHANCES MAINLY IN THE
AFTERNOONS AND EARLY EVENINGS BY MIDWEEK. PERIODIC RESTRICTIONS
REMAIN POSSIBLE.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...CAC
NEAR TERM...CSH/WIMBERLEY
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...WIMBERLEY
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