Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 151823

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
123 PM EST Wed Nov 15 2017

A weak cold front crosses our region early Thursday. A strong cold
front crosses the area over the weekend with much cooler
temperatures to start next week.  Cool high pressure will be the
dominant weather feature for the first half of next week.


As of 1:15 PM Wednesday...Per latest satellite imagery, stratus
cloud deck from this morning has finally dissipated, as cirrus
continues to increase ahead of an approaching cold front. Expect
high temperatures to climb a few more degrees this afternoon
before capping off at our daytime high`s. No major adjustments
made in going forecast attm.

Otherwise, a more amplified upper trof will continue to dig
down across the Great Lakes today. The trof axis will remain to
our north as it moves eastward, approaching New England by the
end of the period, 12z Thursday. At the sfc, high pressure will
remain centered over Northern New England as another cold front
approaches the fcst area from the west. The front is expected to
move into the CWFA in the 00 to 03z Thurs timeframe and
transition thru the area fairly quickly. By the end of the
period at 12z, all of the model guidance has the bndy east of
the CWFA. The fropa is expected to be mostly dry with fairly
shallow moisture associated with it. As such, I kept the slight
chance to solid chance PoPs relegated to the higher terrain and
foothills. By roughly 12z, PoPs are back below slight chance.
Temps should remain below climatology again today with highs
topping out below 60 degrees over all zones. Lows tomorrow
morning should be near normal for mid-November with the higher
terrain seeing slightly above normal values as low-lvl winds
become more SLY later tonight.


As of 215 AM EST Wednesday: Upper trough axis will be in place over
the area at the start of the short term, with a surface front off
the coast and a bit of NW flow moisture against the mountains.
Chances of any precip coming out of this is looking less and less,
with deep moisture really lacking, having lifted to the north. If
anything does fall after 12z Thursday, temperatures look to remain
above freezing so any light showers or sprinkles would be liquid.
Despite being behind the front, temperatures on Thursday will
increase several degrees over today since the cool high pressure in
place at the surface will be scoured out, and northwesterly low-
level flow will add the downsloping component to the clear skies,
allowing temperatures to rise to near, if not a degree or so above,
seasonal normals. Surface high pressure moving from the MS Valley to
the East Coast will dominate the area through the rest of the
period, as shortwave ridging increases Friday ahead of a stronger
wave to affect us over the weekend. Slightly cooler on Friday as the
high brings winds around from the NE again.


As of 230 AM EST Wednesday: Operational guidance is finally starting
to come into better agreement for the weekend system, with the 00z
GFS slowing the front down a tad and the 00z ECMWF speeding it up.
Still looking at a sharp, positively-tilted trough pushing across
the middle of the country on Saturday, with a strong surface low
working its way across the Great Lakes. High pressure that was over
the Carolinas at the end of the short term will push into the
western Atlantic and as the surface trough approaches, the gradient
will increase strongly ahead of the front. Low-level WAA will allow
temperatures to warm a few degrees higher than those on Friday, with
near seasonal temperatures expected overall. With the strengthening
gradient, winds will pick up out of the SW through the day, and pops
will be on the increase. With the slower trend, highest pops now
look to be Saturday evening rather than afternoon. Instability looks
minimal with the system so have continued trend of keeping wording
at all showers. With the slower progression of the front,
temperatures Saturday night continue to inch higher, and likely
it`ll be a fairly rapid decrease just before or at sunrise to the
overnight low. The overlap between the freezing temperatures and
moisture is not very long, as the frontal precip will be exiting by
sunrise, leaving just some NW flow moisture, which of course remains
limited to the higher elevations (>3500ft) of the NC mountains.
Cannot rule out some minor accumulations especially along the TN

Deep-layer CAA behind the front will settle in for the beginning of
the week, with clear and cold (8-10 degrees below normal) conditions
through the end of the period. Winds will still be kind of breezy on
Sunday immediately behind the front, but will diminish Monday into
Tuesday as high pressure settles across the area. Right now the
coldest night looks to be Sunday night, with lows in the mid 20s
across the mountains and at or below freezing everywhere else. There
has already been some talk about this, but it does look like another
(and at this time mainly dry) front will push through the area just
beyond the end of the period, likely keeping temperatures below
normal through Thanksgiving.


At KCLT and Elsewhere: Expect VFR to prevail through the 18Z TAF
period. Lingering stratus deck affecting KAVL/KHKY/KAND earlier
today has since dissipated, giving way to FEW/SCT cirrus across the
entire area with light SW winds this afternoon. Expect this trend to
continue over the next few hours as cloud cover will gradually begin
to increase west to east this evening ahead of an approaching weak
cold front. Limited moisture will accompany this system, but would
not entirely rule out a few light showers at KAVL/KHKY between 02-
05Z. However, do not anticipate any restrictions as a result. After
daybreak, VFR will persist behind the front as cloud cover gradually
decreases and light and variable winds become southwesterly around
13-15Z, increasing to 5 to 8 kts.

Outlook: Potential for MVFR/IFR with a cold front on Saturday as
increased cloud cover and widespread SHRA may allow for reduced
vsbys/cigs. Otherwise expect VFR.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High  87%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  94%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     Low   58%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High  94%     High 100%     High 100%     High  83%

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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