131
FXUS62 KGSP 171800
AFDGSP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
200 PM EDT WED SEP 17 2025
SYNOPSIS
WEAK HIGH PRESSURE BUILDS OVER THE SOUTHEAST THROUGH SATURDAY BEFORE
STRONGER HIGH PRESSURE BUILDS OVER THE REGION LATE THIS WEEKEND INTO
EARLY NEXT WEEK, ALLOWING MOSTLY DRY CONDITIONS TO CONTINUE. EXPECT
A WARMING TREND INTO FRIDAY BEFORE A COOLING TREND RETURNS BRIEFLY
THIS WEEKEND. CLOUDINESS AND CHANCES FOR RAIN SLOWLY INCREASES
TOWARD THE MIDDLE OF NEXT WEEK.
NEAR TERM /THROUGH THURSDAY/
AS OF 118 EDT WEDNESDAY...
KEY MESSAGES
1) VERY ISOLATED SHOWERS ACROSS THE NORTH CAROLINA MOUNTAINS AND
SAVANNAH RIVER VALLEY THIS EVENING.
2) MOSTLY CLEAR AND DRY CONDITIONS TONIGHT.
3) MOSTLY DRY ON THURSDAY, WHILE TEMPERATURES BEGIN TO WARM UP.
QUIET WEATHER IN STORE FOR THE REMAINDER OF TODAY AND TOMORROW.
A WEAKENING SURFACE LOW ANALYZED OVER THE CHESEAPEAKE BAY
REGION WILL CONTINUE LIFTING NORTH UP THE MID-ATLANTIC COAST,
LEAVING IN ITS WAKE NEBULOUS HIGH PRESSURE OVER THE CAROLINAS.
OPERATIONAL GUIDANCE DEPICTS A WEAK VORT LOBE DIPPING DOWN OFF THE
CUMBERLAND PLATEAU THIS AFTERNOON AND MOVING ACROSS THE SMOKIES
AND BALSAMS INTO NORTHERN GEORGIA THROUGH LATE THIS EVENING.
SIMILAR TO YESTERDAY, CAMS DEPICT SOME 500-900 J/KG SBCAPE
DEVELOPING WEST OF I- 26, BENEATH THE ADVANCING SHORTWAVE...BUT
FORCING IS APPARENTLY WEAK ENOUGH THAT MODEL CONSENSUS DOESN'T
FORECAST MUCH CONVECTIVE COVERAGE. LAPSE RATES ARE ADMITTEDLY QUITE
POOR IN FORECAST SOUNDINGS, AND DESPITE THE ADVANCING SHORTWAVE,
PROFILES AT AVL DEPICT BORDERLINE-CAPPING...WHICH MIGHT SERVE TO
EXPLAIN THE LACK OF RESPONSE IN HI-RES GUIDANCE. NONETHELESS, VERY
ISOLATED SHOWERS WILL PROBABLY OCCUR SOMEWHERE OVER THE WESTERN
1/3 OF THE FORECAST AREA THIS AFTERNOON AND EVENING. OTHERWISE,
HIGHS SHOULD BE A TAD WARMER THAN YESTERDAY'S ACROSS THE UPSTATE,
AND SIMILAR TO YESTERDAY'S ACROSS MUCH OF NC...CLIMBING INTO THE
LOW 80S ACROSS THE LOW TERRAIN.
TONIGHT, FOLLOWING THE PASSAGE OF THE SHORTWAVE, SLOW CLEARING IS
EXPECTED. HEIGHTS WILL BEGIN TO RISE, SUCH THAT DESPITE ANOTHER
ROUND OF GOOD RADIATIVE COOLING, LOWS WILL LAND A CATEGORY WARMER
THAN THIS MORNING - IN THE UPPER 50S TO LOWER 60S OUTSIDE THE
MOUNTAINS. HIGHER ELEVATIONS COULD FALL INTO THE 40S. TOMORROW,
SHORTWAVE RIDGING WILL CONTINUE TO BUILD OVER THE AREA, SUPPRESSING
PROFILES FURTHER AND LEADING TO ANOTHER CONVECTIVELY-QUIET AFTERNOON
DESPITE AT LEAST ~500 J/KG SBCAPE DEVELOPING OVER THE MOUNTAINS
AGAIN. THURSDAY AFTERNOON HIGHS WILL CONTINUE THE WARMING TREND,
HITTING AT LEAST THE MID-80S ACROSS THE FORECAST AREA.
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/
AS OF 120 PM EDT WEDNESDAY...
KEY MESSAGES:
1) MOSTLY DRY WITH VERY WARM DAYS.
2) HIGHS ABOVE NORMAL, LOWS NEAR NORMAL.
3) POPS FOR DIURNAL CONVECTION MAY NEED TO BE INCREASED IN FUTURE
UPDATES.
A WEAK TROUGH WILL REMAIN CENTERED OVER THE REGION THROUGH THE SHORT
TERM, ALTHOUGH HEIGHTS WILL REMAIN ANOMALOUSLY HIGH, RESULTING IN
VERY WARM CONDITIONS, ESPECIALLY DURING THE DAY, WHEN MAX TEMPS ARE
FORECAST TO BE ALMOST 5 DEGREES ABOVE CLIMO ON FRI AND SAT. THE
HEAT COMBINED WITH MARGINAL LEVELS OF MOISTURE ARE EXPECTED TO
RESULT IN MODEST AFTERNOON INSTABILITY. AS SUCH, THE NAM REMAINS
SOMEWHAT BULLISH IN TERMS OF DIURNAL DEEP CONVECTIVE DEVELOPMENT,
ESPECIALLY ON SATURDAY AFTERNOON. MEANWHILE, THE LATEST RUN OF
THE GFS IS BEGINNING TO TREND IN THE DIRECTION OF A MORE ACTIVE
LATE-WEEK AS WELL. FOR NOW, HAVE OPTED TO CONTINUE ORIENTING OUR
FORECAST TOWARD A DRIER SCENARIO, BUT IF MODEL TRENDS CONTINUE ON
THEIR CURRENT TRAJECTORY, POPS WILL NEED TO BE INTRODUCED/INCREASED
IN LATER UPDATES.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
AS OF 130 PM EDT WEDNESDAY...
KEY MESSAGES:
1) TEMPERATURES COOLING TO NEAR-NORMAL EARLY NEXT WEEK BEFORE
WARMING AGAIN.
2) BREEZY WINDS DEVELOP ON SUNDAY, MAINLY EAST OF THE MOUNTAINS
3) CONFIDENCE IS BELOW NORMAL REGARDING THE PATTERN DETAILS AND
THE IMPACT ON PRECIP POTENTIAL DURING THE LATTER HALF OF THE PERIOD.
INVERTED SURFACE RIDGING WILL DEVELOP DOWN THE EASTERN SEABOARD
SAT NIGHT INTO SUNDAY AS 1030-ISH MB HIGH PRESSURE BUILDS INTO NEW
ENGLAND. ATTENDANT ADVECTION OF DRIER AND COOLER AIR WILL RESULT IN
ESSENTIALLY PRECIP-FREE CONDITIONS, WITH TEMPS MAX TEMPS MODERATING
TO NEAR-NORMAL LEVELS SUNDAY INTO MONDAY. SURFACE RIDGE WILL WEAKEN
EARLY IN THE NEW WORK WEEK, AS SURFACE HIGH PRESSURE CENTER
PROGRESSES WELL OFF THE NEW ENGLAND COAST. BEYOND MONDAY, THE
DETAILS BECOME MURKY, AS THE GLOBAL MODELS AND ENSEMBLE SYSTEMS
DIVERGE IN THEIR HANDLING ON AN AREA OF LARGE-SCALE HEIGHT FALLS
OVERSPREADING THE CENTRAL CONUS MON NIGHT/TUE. SOME GUIDANCE
RESPONDS WITH UPGLIDE AND DEVELOPING ONSHORE FLOW ATOP WEAKENING
SURFACE STABLE LAYER AND PRECIP DEVELOPMENT OVER THE SOUTHEAST
DURING THIS TIME FRAME...WHILE OTHER SOURCES DEPICTING WEAKER OR
FARTHER WEST OR NORTH HEIGHT FALLS MAINTAIN GENERALLY DRY
CONDITIONS. IN LIGHT OF THIS UNCERTAINTY, IT SEEMS PRUDENT TO ALLOW
POPS TO STEADILY TREND TOWARD A TOKEN 20-30% RANGE BY THE MIDDLE OF
NEXT WEEK. TEMPS ARE FORECAST TO RETURN TO SLIGHTLY-ABOVE NORMAL
LEVELS BY WED, BY WHICH POINT THE SURFACE RIDGE/LOW LEVEL ENE FLOW
IS EXPECTED TO DISSIPATE.
AVIATION /18Z WEDNESDAY THROUGH MONDAY/
AT KCLT AND ELSEWHERE: VFR ON TAP TODAY AS WEAK HIGH PRESSURE
REMAINS IN CONTROL OF THE FORECAST. MOST TERMINALS ARE EXPERIENCING
A LIGHT N/NW WIND, WITH THE EXCEPTION OF A FEW SITES ACROSS THE
PIEDMONT REPORTING A WSW WIND INSTEAD. EXPECT PREDOMINANTLY N
WINDS THROUGH THE PERIOD, WITH FEW/SKC CLOUD COVER THE REST OF
THE DAY. CAN'T RULE OUT ISOLATED SHOWER ACTIVITY THIS AFTERNOON,
MAINLY OVER THE MOUNTAINS, BUT COVERAGE IS EXPECTED TO BE FAR TOO
LOW TO WARRANT A MENTION IN THE KAVL TAF. OVERNIGHT, WINDS WILL
GO VARIABLE BEFORE PICKING UP FROM THE NORTH IN THE MORNING.
ONCE AGAIN, MOUNTAIN VALLEY FOG AND STRATUS LOOK LIKELY, AND
RESTRICTIONS ARE ADVERTISED AT KAVL. AFTER DAYBREAK, SOME FEW/SCT
CU WILL BREAK OUT, BUT SHOULD AMOUNT TO LITTLE IF ANY CONVECTION,
EVEN OVER THE MOUNTAINS.
OUTLOOK: DRY CONDITIONS EXPECTED THROUGH SUNDAY. SOME MOUNTAIN
VALLEY FOG WILL REMAIN POSSIBLE EACH MORNING WHEREVER CLOUDS DO
NOT INHIBIT NOCTURNAL RADIATION.
GSP WATCHES/WARNINGS/ADVISORIES
GA...NONE.
NC...NONE.
SC...NONE.
SYNOPSIS...DEO
NEAR TERM...MPR
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...MPR
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