Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 240332
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1032 PM EST Tue Jan 23 2018

.SYNOPSIS...
Dry high pressure will overspread the region and persist into the
end of the work week. Another cold front will bring rain to the
region over the weekend, with drying expected next week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 1030 PM EST...Not much seen at the moment on radar along
the TN border, but some upstream light returns suggest that it
is a good idea to have a small precip prob in that area. Winds
have increased, especially over the nrn mountains, so the Wind
Advisory also looks like a really good course of action. Other
than adjusting for temp trends, as temps are falling off slower
than expected, the fcst looks good.

Otherwise...an upper trough will continue to lift across the eastern
Great Lakes to the St. Lawrence Valley tonight, pushing a cold
front well east of the area. Low-level flow should veer to NWLY
thru this evening. As it does, sfc winds should diminish somewhat
and lose the strong gusts outside the mountains, but actually
pick up a bit in the high terrain. The current Wind Advisory for
the Northern Mountains thru 15z Wed looks good. The NW flow will
also bring a cloud deck up against the TN/NC border areas, with
a few snow showers possible. Snow accums should be very light,
generally a dusting to up to half an inch. Other that those low
clouds, only a few wisps of cirrus are expected overnight. Temps
will return to near normal with lows in the 20s in the mtns and
lower to mid-30s across the piedmont.

Wednesday, sfc high pressure will build in from the west and should
bring in drier and dissipate the NW flow clouds and snow showers
by early aftn. Winds should be much lighter, especially east of the
mtns. Under sunny to mostly sunny skies, highs will be a category or
two below normal in the mtns and near normal in the piedmont. Highs
mainly in the 40s mtns and lower to mid-50s piedmont.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 155 PM EST Tuesday: Heights rise through the period as a short
wave moves east of the area Wednesday night and a ridge axis builds
in by Friday. The last of the breezy conditions and NW upslope flow
clouds across the mountains come to an end Wednesday night as high
pressure builds in from the west. The center of the high moves
across the area Thursday then to our east Friday but high pressure
remains ridged into the area from the east. Lows a little below
normal Wednesday night rise to around normal Thursday night. Highs a
few degrees above normal Thursday rise to around 5 degrees above
normal for Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 200 PM EST Tuesday: The medium range forecast picks up Friday
night with the area under the waning influence of a surface high
centered off the east coast near Bermuda. Surface winds will veer
around from the southeast ahead of an approaching upper trough and
surface cold front, gradually moistening the atmospheric column. On
Saturday, guidance disagrees somewhat on the onset of precipitation,
though some light rain in the normal favored upslope areas near the
Blue Ridge escarpment appears likely at this point, with isolated
precip in all other locations in the forecast area becoming more
likely as Saturday wears on. The bulk of the pre-frontal precip will
arrive on Sunday, with widespread showers expected across the entire
area. Forcing and shear will be quite good on Sunday afternoon, but
instability, especially surface-based instability, will be very
limited. Nonetheless, the front and upper trough will be dynamic
enough that this portion of the forecast should be watched closely
over the next few days. There is still some disagreement of the
exact evolution of the surface front and the potential for the
development of a Gulf low on Sunday, so QPF is still in question,
though no major global model has particularly threatening weekend
rainfall totals at the moment.

Guidance remains in disagreement on the speed of the front as well,
though major models do agree that precip will come to an end by 12Z
Monday morning, with the exception of some light lingering NW flow
snow. Temperatures will be almost 10 degrees above average ahead of
the front on Sunday before dropping to near average Monday through
the rest of the period after the frontal passage.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
At CLT and elsewhere, except KAVL...VFR through the period. The
cold front/wind shift was just NW of the air field at issuance
time, thus the immediate change group at 0030Z to bring the wind
around to NW. Other sites should see a more gradual change to
NW this evening. Dry high pressure will build in behind the cold
front with only a few cirrus moving overhead. Wind will diminish
in the pre-dawn hours and remain light into mid/late morning. A
lee trof may develop again on Wednesday, which will bring the
wind back around to WSW in the afternoon, with occasional gusts
possible. Wind will go light WNW again with sunset Wednesday.

At KAVL...Wind will be out of the NW thru the period and should
remain gusty. There is also a chance that some low-VFR or possibly
MVFR stratus works up the valley overnight, as flow turns out of the
NW. For now, will highlight some sct040 during the overnight hours.

Outlook: Dry high pressure will dominate the area through the
remainder of the week. Another system will move in over the weekend,
bringing another round of -SHRA and restrictions.

Confidence Table...

            03-09Z        09-15Z        15-21Z        21-00Z
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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Wind Advisory until 10 AM EST Wednesday for NCZ033-049-050.
SC...None.

&&

$$
SYNOPSIS...Carroll
NEAR TERM...ARK/PM
SHORT TERM...RWH
LONG TERM...Carroll
AVIATION...PM


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