Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 240535

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1235 AM EST Fri Nov 24 2017

Dry high pressure will remain across the region during the next
couple of days. A fast-moving cold front may bring a few showers to
the mountains by Saturday. Another area of dry high pressure builds
in after the front and will persist into the middle of next week.


As of 1230 AM EST: Surface low pressure centered east of
Jacksonville, FL early this morning will move northeast away from
the coastal Carolinas through the day. Meanwhile, an upper level
trough axis along the Appalachians will will move east to the coast
today as the upper flow pattern gradually deamplifies and becomes
more zonal through tonight. A little cirrus may arrive on the
westerly flow aloft tonight. Temperatures should recover to slightly
above climatology in most areas for afternoon maxes and overnight


As of 130 PM EST Thanksgiving Day: The period will begin with high
pressure in place underneath weak troughing over the coast, with
another sharp shortwave coming across the Great Lakes. As we move
toward Saturday morning, the Great Lakes trough will deepen and push
east, with the southern reaches of the moisture just making it into
the NC mountains. The front pushes across the area during the day,
getting hung up in the mountains as is typical, but then will move
east of the area by Saturday evening. Not much moisture at all to be
squeezed out of this system, with the GFS and NAM remaining the
wettest of the operational models (and even then it`s not all that
impressive). Have continued trend of slight chance pops along the
state line in the middle of the day, but really just a quick shot of
some light showers. Overall, Saturday looks like an incredibly nice
day for most of the area, with highs across the Piedmont in the mid
60s, down to the upper 40s at the mountaintops, really about 2-3
degrees above seasonal normals.

The front passes by and cool high pressure builds in from the west
Saturday night into Sunday. Should see a brief uptick in winds
across the mountains Saturday night as the gradient tightens
somewhat. The cooler airmass will result in temps below normal by
about 2-3 degrees, but again really quite nice for Thanksgiving


As of 145 PM EST Thanksgiving Day: Most of the extended is very
quiet, with a slow warming trend as the high pressure (that begins
to ridge into the area at the end of the short term) moves over the
region and modifies. Troughing will remain dominant over the Eastern
Seaboard, though by Tuesday morning ridging will build over the
southern states, moving over the Southeast coast by Wednesday. This
plus the low-level southerly flow will allow temperatures to slowly
climb from a few degrees below-normal to start the period to a few
degrees above by Wednesday, with plenty of sun to go with it. Coldest
night looks to be Sunday night in the wake of the weekend front.

As we`re enjoying the pleasant weather through the middle of the
work week, a cutoff low over the Rockies will push into the Plains,
sliding east through the end of the period. The good thing is that
the GFS has trended much closer with the ECMWF as far as the overall
look of the mass fields, but it is faster with progression of the
system. It initially has this cutoff low phased with a transient
shortwave crossing the northern tier, while the ECMWF keeps it its
own entity and doesn`t move it into the Plains until Wednesday
evening (the GFS has it over the Mid-South at this point). The GFS
then keeps the low cut off through the end of the week, whereas the
ECMWF absorbs it into a digging trough coming out of Canada, and in
general keeps it a little farther north with fewer impacts to our
area. The GFS would bring precip into our area overnight Wednesday
night, keeping activity around through the end of the day Thursday.
Have delayed onset of pops and have kept pops much lower than
guidance given these uncertainties. Also, with forecast lows in the
mid 30s Wednesday night across the mountains, this might lead to a
little mixed p-type in these areas, so have kept some light
rain/snow mix in the forecast.


At KCLT and elsewhere: Light to calm winds and clear skies will
continue through the morning hours. Some patchy valley fog could
form in the southwest NC mountain valleys toward daybreak, otherwise
VFR conditions are expected. A light southerly flow should develop
through the day, with FEW to SCT cirrus encroaching from the west
the latter half of the period.

Outlook: Expect mainly VFR conditions through the forecast period as
dry/cool conditions prevail.

Confidence Table...

            05-11Z        11-17Z        17-23Z        23-00Z
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:




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