000
FXUS62 KGSP 271837
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
237 PM EDT Mon Sep 27 2021

.SYNOPSIS...
Dry high pressure will dominate the region through Tuesday, with
warming temperatures. A back door cold front will approach from the
Mid-Atlantic region on Wednesday and move south of the area by late
in the week. Another cold front may approach from the northwest
by early next week, with better moisture possible.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 130 pm: Upper trough will remain centered near the East Coast
through the period, while surface high pressure will remain centered
off the Carolina coast. Continued SW low-level flow and building of
a strong upstream ridge into the area will yield continued dry
weather with a warming trend, with min temps tonight expected to
average just a few degrees below normal, while maxes Tuesday are
expected to be a solid 5 degrees above climo. Otherwise, fog and low
stratus will redevelop across the mountain valleys and many lakes
and rivers outside the mountains during the pre-dawn hours before
burning off between sunrise and late morning.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EDT Monday: No significant changes made to the short
term. A potent trough will dive south out of Canada to the New
England coast Wednesday into Thursday. An associated back door cold
front will probably hang up near the area as better forcing pushes
offshore and the front itself becomes parallel with the northwest
flow aloft. As such, any significant cooling with the front will
probably hold off until early in the extended period. Mostly sunny
skies will prevail, except possibly in the vicinity of the front as
it edges into the region from the north. A steep surface based
inversion late early each morning may support fog or low clouds
focused across the mountains. Highs will likely be above normal in
the 80s with overnight lows a bit above normal as well.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 235 PM EDT Monday: Forecast uncertainty remains above normal
during the extended period. Friday or Saturday are probably the most
likely days for a wedge pattern to take hold with modest high
pressure building into the Mid-Atlantic states. Although with below
normal confidence in the possible wedge configuration, opted to only
lower temperatures a touch below guidance, in line with neighboring
offices. Skies will be mostly sunny through Saturday except perhaps
near the wedge boundary and slowly increasing high clouds.

An assortment of weak 500 mb lows may interact across the Central
States and gradually break down long wave ridging over the area
thing weekend into early next week. The 12Z operational GFS seems
entirely too aggressive in doing this (even compared to many of its
ensemble members) and therefore is thrown out. Sunday, Increasing
moisture out of the west and possibly associated with the wedge
boundary as it lifts back north as a warm front will increase cloud
cover with a slight chance of showers remaining in the forecast
north of I-85. Shower chances and cloud cover may continue to
increase into early next week with a broad trough to our west
injecting additional moisture via southwest flow aloft. Near to
slightly above normal temperatures seem like the best bet given the
expected pattern.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Persistence is the name of the day, as VFR
conditions will persist through much of the next 24-36 hours, with
the exception of a return of fog/low stratus in the mountain valleys
early Tuesday morning. While restrictions were widespread this
morning, the fog/low stratus remained just out of reach of KAVL
through the morning. That being the case, opted to limit the KAVL
forecast to 3SM/SCT003 between 09-13Z. As has been the case the past
couple of mornings, fog/low stratus will likely develop on Lakes and
rivers in the foothills early Tuesday as well, but it`s very
uncertain if any of this will drift over the terminals (KAND/KHKY
primarily), so will forecast VFR at all other sites through the
period. Winds will generally favor light SW.

Outlook: Mostly VFR conditions are expected to persist through the
week. However, mountain valley fog is likely each morning.

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...JDL
SHORT TERM...Munroe
LONG TERM...Munroe
AVIATION...JDL

NWS GSP Office Area Forecast Discussion