110
FXUS62 KGSP 181354
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
954 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/...
1000 AM Update...No sigfnt changes made the fcst grids. A cutoff
upper low continues to provide enuf lift to produce periods of -ra/dz
over most areas and expect little improvement thru the next update.
Temps and td/s are holding nearly steady-state in this moist environ
with only slow warming thru the remainder of the morning due to
widespread downcast conds.

The upper 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 /14Z 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/SBK
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...ARK