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192
FXUS62 KGSP 180711
AFDGSP

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

.SYNOPSIS...
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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.
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&&

.NEAR TERM /THROUGH TONIGHT/...
As of 200 AM EDT Wednesday: 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/...
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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.
-- End Changed Discussion --

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Continued messy TAFs, as a remnant low
spins over the forecast area. The center of the low is near the
GMU/GSP sites, so LIFR conditions are expected to persist thru
mid-morning. Missing obs across the mountains (and especially
at KAVL), makes for very low confidence fcst for KAVL. Went
with guidance on LIFR conditions and potentially some fog thru
mid-morning. The other sites are on the edges of the circulation,
and may have more variable conditions. KCLT is starting out VFR,
but is expected to see at least some MVFR cigs this morning,
which 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 areas of fog and low stratus forming
again tonight. 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