FXUS62 KGSP 231120
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
620 AM EST Thu Nov 23 2017
Dry high pressure will persist over the area over the next couple
of days. A fast-moving cold front may bring a few showers to the
mountains Saturday. Another dry surface high builds in thereafter,
persisting into the middle of next week.
.NEAR TERM /THROUGH TONIGHT/...
As of 620 AM EST Thursday: An upper trough builds into the
southeastern US today. The southerly jet stream flow ahead of this
trough is keeps widespread cirrus over the area this morning. The
cirrus diminishes this afternoon as the trough and jet stream move
east. At the surface, high pressure builds into the area from the NE
as an inverted trough develops over central GA. Southerly low level
flow around the high and trough will bring some shallow low level
moisture into the NE GA and the western Upstate. This should create
some stratocu moving north across those areas this morning which
dissipate through the afternoon as the high and trough weaken. All
this to say the dry and mostly sunny but cool forecast continues.
Highs will be around 5 degrees below normal.
Weak high pressure remains over the area tonight as the upper trough
axis moves into the area. Mostly clear skies are expected but
mountain valley fog could develop overnight. Lows will be a few
degrees below normal.
.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
As of 130 AM Thu: A weak sfc ridge will sit over the region Friday,
even as a shortwave to our south maintains an area of low pressure
off the Southeast coast. Consensus of the operational models is
for this low to remain far enough offshore that only the Lowcountry
would be affected by any precip. A small contingent of SREF members
does show precip spreading up into the I-85 corridor, but this
does not lend enough confidence to warrant a mention in the fcst.
Early Saturday, a mature low pressure system will move across
James Bay, pulling a broad trough and cold front across the eastern
CONUS. For several days models have depicted this front as bringing
barely enough moisture to expect precip, and the latest runs
continue the trend. The GFS is the wettest--but it only wrings out
a few hundredths Saturday afternoon/evening. A slight chance of
showers has been included as a result. In the wake of the front,
dry high pressure expands into the area through early next week.
Temps will trend warmer from Fri to Sat, going from around normal
to about a category above normal. The mtns will see temps turn
colder Saturday night behind the front, with the remainder of
the area not seeing cooler temps until the high builds in Sunday,
resulting in mins a few degrees below normal Mon morning.
.LONG TERM /MONDAY THROUGH WEDNESDAY/...
As of 300 AM Thu: Sfc high pressure becomes centered off the East
Coast late Monday, turning the flow southerly. Meaningful moisture
return will take some time, though a warming trend will begin
and continue into midweek. The high will lose influence on our
area by Wednesday, though model solutions diverge as to what comes
next. The North American models show a fairly deep trough and cold
front reaching the southern Appalachians Wednesday morning. The EC
features separate troughs in the northern and southern streams;
the northern one is timed similar to the one depicted by the
GFS and Canadian, but without the pronounced front. The EC's
southern wave then reaches our area Thursday. The fcst package
mainly will reflect the solutions of the North American models,
with PoPs increasing gradually from Tuesday night onward. Though
temps will be too warm for anything but rain at onset, temps cool
enough by early Thu that snow is mentioned in the mtns.
.AVIATION /11Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Dry high pressure over the area will result
in mostly VFR conditions through the period. Clouds should primarily
be limited to SCT-OVC high clouds. However, some stratocu in the 040-
050 range will approach KAND 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. Better chances for
mountain valley fog Friday morning.
Outlook: Expect mainly VFR through the forecast period as dry/cool
11-17Z 17-23Z 23-05Z 05-06Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% 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:
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