Area Forecast Discussion
Issued by NWS Greer, SC

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198
FXUS62 KGSP 020301
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1001 PM EST Thu Dec 1 2016

.SYNOPSIS...
Dry and cooler conditions will persist through Saturday. Moisture
should return from the west for the latter half of the weekend and
possibly linger into early next week.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 955 PM EST: Temperatures were running a bit above forecast
late this evening, but gradual decoupling of the winds should permit
temperatures to fall more quickly through the early overnight. No
changes in minimum temperatures are thus needed. Otherwise, surface
high pressure will build slowly east to the southern Appalachians
overnight beneath developing quasi-zonal flow aloft. Drier/cooler
air advecting into the region will lead to lowering of
temps/dewpoints through the period amidst modest sfc/llv westerly
flow. Minimal llv moisture will continue to lift orographically
along the TN line leading to a few upslope induced clouds overnight,
while the remainder of the fcst area remains clear. Diurnal cooling
will allow temps to fall back to near normal levels by morning,
warming to normal for highs on Friday. Skies will remain mostly
sunny on Friday, with the exception of a few high cirrus streaming
in aloft along the mean westerly H5 flow.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 215 PM EST Thursday: Upper ridge builds in through Saturday
night then slides east on Sunday with weak short waves moving over
the area through the flow during this time. At the surface, high
pressure noses in from the northwest through Saturday night, with
the center of the high settling over NC on Sunday. Clouds increase
over the area through the period as mid and high level moisture move
in. Low level moisture and isentropic lift move into the mountains
and Upper Savannah River valley Saturday night and spread east on
Sunday. There is still some discrepancy in the guidance on the
location of best moisture, lift and resulting precip both periods.
Therefore, have gone with a model blend which brings likely PoP into
the SWRN NC Mountains and NE GA Mountains Saturday night. PoP
increases to categorical over these areas Sunday, with likely PoP
spreading across much of the area west of the I-77 corridor. Temps
and forecast soundings for Saturday night show the potential for
precip to mix with snow across the higher elevations of the NC
Mountains. Given the light precip amounts, do not expect any
accumulations for now. Highs will be near to slightly below normal
Saturday, then fall to around 10 degrees below normal Sunday. Lows
follow the opposite pattern.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
At 2 PM Thursday: On Sunday evening an upper ridge will be along the
east coast, while a closed upper low will be over Northern Mexico.
On Monday the original ridge breaks down, and northern forms to its
west from FL to the Great Lakes, while the upper low moved from
Mexico to Texas. The upper ridge reaches the East Coast by Friday,
while the upper trough weakens and reaches the TN River Valley. The
upper low weakens as it crosses the upper ridge. By Wednesday the
models disagree on the position of the ridge, having either along
over the Eastern USA, or off the East Coast, while a trough
amplifies over the Rockies or the Plains. This discrepancy continues
into Thursday, when the upper trough is either over the Plains, or
extends from the Great Lakes to the Gulf States.

At the surface, on Sunday evening a surface ridge will be located
along the Eastern Seaboard. Moist isentropic upglide and upslope
flow from the Gulf of Mexico will support precipitation production
over the Western Carolinas and Northeast Georgia. The surface ridge
moves off the coast overnight, but is replaced by another ridge on
Tuesday. Meanwhile, upglide and upslope floe continue ahead of a
cold front crossing the lower MS River Valley. This front reaches
our area early on Tuesday, crossing the area during the day. The
models disagree on whether surface ridging remains in the wake of
the front on Wednesday, and on the timing of the arrival of another
front that arrives on Wednesday night or Thursday, as well as the
amount of moisture accompanying the boundary. Temperatures will
exhibit a reduced diurnal range, with maximums below normal and
minimums above normal.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: VFR continues through the period as high
pressure builds in from the west leading to cooler/drier air
advecting into the region. Expect skies to remain mostly clear with
the exception of a few high cirrus streaming in. Winds are expected
to remain briefly WSW early this evening before quickly veering back
WNW later this evening. Given continuation of the llv/mlv pattern on
Friday, expect some measure of lee trof development again. Will
feature some WSW flow at the foothill sites but omit it from KCLT
for now. NW flow will see occasional low end gusts at KAVL with the
surface high still west of the mountain chain.

Outlook: Dry high pressure will persist over the region through
Saturday. Precip and restrictions may return as soon as Sunday as
another cold front moves into the region. Low pressure may develop
along the front to our west and bring a second shot of moisture into
the region Monday night into Tue.

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...None.
SC...None.

&&

$$
SYNOPSIS...CSH
NEAR TERM...HG
SHORT TERM...RWH
LONG TERM...JAT
AVIATION...HG



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