597
FXUS62 KGSP 181049
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
649 AM EDT Wed Sep 18 2024

.SYNOPSIS...
The remnants of the coastal low will meander over the region today
and dissipate by Thursday. Meanwhile, high pressure begins to build
into the region from the north and west giving our region a dry
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 645 AM EDT Wednesday: No major change with this update. Light
showers are popping up across the southern Upstate and eastern SC
Piedmont, which may affect the Charlotte area this morning. That
will make for a dreary start to the day. But rainfall amounts are
very light. Less fog than earlier expected, with the exception of
the Greenwood to Laurens area.

Otherwise, the remnant low associated with Potential Tropical
Cyclone Eight is centered roughly over the central Upstate, and
will begin to drift slowly east today. The weakening low should
support a little more mixing and some breaks in the clouds later
in the day, which will help high temps to rebound from yesterday`s
readings. The warmer temps and still cool temps aloft will support
at least a few hundred J/kg sbCAPE by midafternoon, especially
around the edges of the low (that is, the northern and eastern parts
of the forecast area). So isolated to scattered showers may develop
before the end of the day (most CAMs show at least some diurnal
convection). Instability and forcing will likely be too weak for
thunder, but cannot rule out one or two general thunderstorms in the
I-40 and/or I-77 corridors. The western and southern parts of the
FA will be on the more stable side of the low. Temps are forecast
to top out a few degrees below normal under mostly cloudy skies.

Tonight, the low will continue to drift east, allowing for most of
the mid and upper moisture to exit stage right. However, lingering
low-level moisture will likely support an increase in low stratus
overnight, with patchy fog possible, especially in the mountain
valleys. Lows will a few degrees above normal.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 135 AM EDT Tuesday: The weak closed upper low will open up
into a shortwave trough by the beginning portion of the forecast
period and lift into the northeast CONUS Thursday night into
Friday as the associated trough axis gradually shifts east of
the CFWA. Upper anticyclone over northern Mexico and Southern
Plains slowly pivots higher heights into the southeastern CONUS in
response to a digging upper low that moves into the southwestern
CONUS. Lingering mid/low-level moisture should keep isolated to
scattered showers across the CFWA on Thursday with a focus on the
mountains and drier conditions becoming more evident elsewhere. The
upper anticyclone axis will begin to encroach the region from the
west as weak high pressure begins to settle in across the area. Dry
air entrainment in the upper and mid-levels of the atmosphere will
essentially shutoff any shower chance outside of a small chance
over the mountains where convergence is maximized. Temperatures
Thursday will be a few ticks below normal for afternoon highs as
cloud cover will be more extensive and that will carry over into
Thursday night as well, with overnight lows a few ticks above
normal. More insolation Friday will result in temperatures rising
to near normal values for highs and better radiational cooling
conditions Friday night leading to near normal temperatures.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 300 AM EDT Wednesday: Upper ridge axis gradually slips east
from the MS Valley to the eastern CONUS over the weekend into the
early part of next week. Surface high stretching from Atlantic
Canada down the Appalachians will control the sensible weather
during this timeframe and allow for a much drier airmass to settle
over the region. Operational models try to send a cold front in from
the west as a shortwave trough travels across the northern CONUS,
but some form of moisture return is evident as the surface high
slips offshore ahead of the front. Mentionable PoPs return to
forecast by D7 as the front inches closer to the area, but of course
uncertainty resides this far out. Temperatures will be near-normal
for mid to late September through much of the forecast period.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Below average certainty in the 12z TAFs,
as a remnant low spins over the forecast area, producing areas of
low CIGS and -RA. The center of the low is over the Upstate, where
LIFR conditions are expected to persist thru mid-morning. Missing
obs across the mountains (and especially at KAVL), makes for very
difficult fcst for KAVL. Went with the LAMP for KAVL and, to some
extend, KHKY. KCLT will be IFR to possibly LIFR this morning with
spotty -SHRA around, then CIGs should lift/scatter out to VFR by
midday. Guidance agrees on scattered showers developing across
the mountains and the NC Piedmont in the aftn, so will carry
PROB30 for those sites. Deep convection/thunder still looks low,
given lack of instability. The low will begin to drift to the
east/north and some clearing of moisture aloft may allow for low
stratus forming again tonight. The latest guidance has backed off
the fog potential, favoring stratus. Winds will be light thru the
period, favoring a NE direction overall.

Outlook: A weak upper low will lift northeast tonight into
Thursday. Restrictions return again tonight thru Thursday morning.
On Friday, sfc high pressure builds into the area from the north
allowing drier weather and VFR conditions to return into this
weekend.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...ARK
NEAR TERM...ARK
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...ARK