Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 230540
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1240 AM EST Thu Nov 23 2017

.SYNOPSIS...
In general, dry high pressure will persist over the area through
early next week. A couple of cold fronts will pass the area
without enough moisture for precipitation. Temperatures will
remain seasonable.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1240 AM EST Thursday: Widespread cirrus will remain over the
area early this morning. Guidance still shows some stratocu
developing across the western Upstate, NE GA, and portions of the
mountains this morning in response to a developing inverted surface
trough.

Otherwise, weather should be nearly ideal for Thanksgiving Day. A
bit of an upper trough digs into the Deep South on Thursday, but
will have little moisture to work with at low-levels, and surface
low associated with it will remain well south of the area. Some high
clouds look to be the only impact from this trough. A large surface
high pressure area will become centered along the mountains by
Thursday morning. Winds through Thursday will thus be much lighter
and somewhat variable. The light winds and very dry near-surface air
should allow for a large diurnal range, with Thu morning`s min temps
likely bottoming out about 5 degrees below climo, or roughly 10
degrees cooler than Wed morning. Thursday will be a dry and crisp
fall day with temperatures slightly above seasonal normal.

Fog that was seen this morning is unlikely on Thursday as BL drying
has dropped dewpoints 10 degrees or so.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
As of 200 PM Wednesday...With sfc high pressure across the area
Thursday night, latest guidance continues to depict the development
of a sfc low in the Gulf of Mexico which is progged to move across
northern FL and hug the FL/GA/Carolina coast throughout the day on
Friday, per the GFS/ECMWF. With split flow, this track would allow
for NW flow aloft to persist across our forecast as seen from fcst
soundings suggesting PWATs to remain at or below one half of an
inch. However, the latest NAM, west of both the GFS and ECMWF,
continues to track this system a bit northward and inland up through
GA/SC. If this track were to evolve, fcst soundings are highlighting
PWATs at or just above one inch. For this forecast package, am going
to stick with the drier trend of the GFS/ECMWF. With nearly clear
skies overnight Thursday, anticipate temperatures to dip into the
low to mid 30`s before climbing into the upper 50`s to around 60
degrees on Friday.

Expect temperatures to be slightly warmer/near-normal Friday night
as limited moisture allows for mid to high clouds to increase ahead
of an approaching cold front. Per latest guidance, anticipate the
front to push through the area Saturday morning. With limited
available moisture and weak forcing, have kept precipitation out of
the forecast attm. As clouds gradually decrease behind the front and
flow aloft becomes nearly zonal, expect temperatures on Saturday to
climb into the lower 60`s, though cooler across the mountains.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 2:15 PM Wednesday: An Upper level northwesterly flow will be
in place Saturday night, following the earlier surface cold frontal
passage. This will signal a trend toward cooler temperatures across
our forecast area (FA) for the latter half of the weekend. The GFS
does show some very shallow moisture in the northern mountains of
North Carolina briefly on Saturday night, but its depth appears to
shallow for any precipitation.

High pressure will move from the Ohio and Tennessee Valleys Sunday,
into our FA Sunday night and Monday. Aloft the flow remains dry
northwesterly, although easing by late Monday.

The surface high will continue moving south and east of the region
Tuesday, while the flow aloft backs to the southwest. This will
signal the start of a warming trend, but still dry.

In the latter part of the forecast the models diverge on how fast to
move a cold front into our area Wednesday. The GFS was fast, while
the European was slower. The slower European was backing and cutting
off parts of the upper level flow. This far out in the forecast
suggests a compromise is in order. We will have some low end POPS in
the mountains and part of the foothills of western North Carolina,
parts of northeast Georgia, and a sliver of the mountains in upstate
South Carolina Wednesday.

Temperatures Wednesday will be tricky depending on how fast any mid
week front enters the picture.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Dry high pressure over the area will result
in mostly VFR conditions through the period. The one exception will
be potential morning mountain valley fog. Clouds should primarily be
limited to SCT-OVC high clouds. However, some stratocu in the 040-
050 range will develop SC terminals and KAVL this morning, as a
shallow layer of lower level moisture sneaks into the area in
association with an area of low pressure developing in the eastern
Gulf of Mexico. NE winds will continue through the morning but will
become light and variable for the afternoon or even toggle to SSE at
KAVL and KHKY. Light and variable winds expected this evening.

Outlook: Expect VFR through the forecast period as dry/cool
conditions prevail.

Confidence Table...

            05-11Z        11-17Z        17-23Z        23-00Z
KCLT       High  81%     Med   72%     High 100%     High 100%
KGSP       Med   75%     Low   55%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High  87%     High 100%     High 100%     High 100%
KGMU       High  81%     Low   55%     High 100%     High 100%
KAND       Med   75%     Med   61%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...JDL/RWH/WJM
SHORT TERM...SGL
LONG TERM...TS
AVIATION...RWH



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