Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 011918

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

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.


As of 115 PM EST Thursday:  A rather quiet near term in store for
the region as high pressure builds in from the west and a cold front
surges out to sea over the western Atlantic, all beneath developing
quasizonal flow aloft.  As such, drier/cooler air advecting into
the region will lead to lowering of T`s/Td`s through the period
amidst modest sfc/llv westerly flow.  With that, minimal llv
moisture will continue to lift orographically along the TN line
leading to upslope induced cu today/tonight, while the remainder
of the fcst area remains mostly sunny/clear through tonight.
Diurnal cooling will allow T`s 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.


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.


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.


At KCLT and Elsewhere:  VFR through the period as high pressure
builds leading to cooler/drier air advecting into the region.
With that expecting skies to remain mostly skc with the exception of
a few high cirrus streaming in.  Winds are expected to remain wswly
this afternoon as lee troffing persists before veering back wnwly
through the overnight hours.  Given continuation of the llv/mlv
pattern on Friday, am once again expecting lee trof development
which could allow for backed wsw flow, however left from taf at
this point.

Outlook: Dry high pressure persists over the region thru
Saturday. Precip and restrictions may return as soon as Sunday,
as another cold front moves into the region. There may be a brief
lull in these impacts Monday, before low pressure develops along
the front to our west and brings a second shot of moisture overhead
Mon night into Tue.

Confidence Table...

            19-01Z        01-07Z        07-13Z        13-18Z
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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