Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 290207
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1007 PM EDT Wed Sep 28 2016

.SYNOPSIS...
A stationary front will remain over the Midlands of South Carolina
and the Sandhills of North Carolina through Thursday.
Meanwhile, an upper level low will drop south into the Ohio Valley
and linger there through the end of the week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 1010 PM Wednesday: The lingering strong convection east of
I-77 will continue moving east and out of the area by midnight.
Drier air has filtered into the western CWFA behind the slowly
moving cold front. No major surprises in the latest model guidance,
with the center of a large upper low moving slowly down across the
Midwest/OH Valley tonight and then over the Cumberland Plateau on
Thursday. The trof axis remains to our west the entire time, with
spokes of vorticity moving around the circulation. This will have a
difficult time pushing the surface front off to the east. Dry air
will filter in from the SW in the dry slot, which should allow for
some cooler temps in northeast GA and the wrn Upstate. However,
there are indications that low level moisture will remain high
across the wrn Piedmont, which could lead to some dense fog around
daybreak. Confidence way too low for any advisories for now.

On Thursday, the upper low is close enough to the mtns such that
more than one fairly strong short wave will pass overhead, along
with some upper divergence. Meanwhile, colder air aloft should
provide some buoyancy. Expect some low-topped convection to develop
in the afternoon over the mtns, so a chance probability will be
kept there. Meanwhile, will also hold onto a chance east of I-77
where the surface boundary will remain. What is interesting is the
lingering severe storm potential seen on the latest Day 2 Outlook.
The drier air filtering in from the SW should keep the convection at
bay over northeast GA and most of Upstate SC. Will bump up high
temps a few degrees for Thursday afternoon on general principles.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 150 PM Wed: Deep upper low remains centered over Kentucky
Thursday night into Friday, then gradually wobbles northward
through Saturday. Heights aloft will have already bottomed out
over our area during this period; upper lapse rates become quite
poor by daytime Friday. Though small precip chances linger over
the northern portion of our CWFA thru Fri mrng, the whole area
is left dry thereafter, with light southerly return flow around
Atlantic high pressure. Mins are expected to be around normal,
with max temps a tad above normal due to plentiful sunshine.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 155 PM EDT Wednesday...At the starting point of 00Z Sunday,
the cut off upper low is forecast to be over NE corner of Indiana.
Other than some cloudiness mainly over the NC Mountains, no sensible
weather for our area. The low will begin to move NE for the rest of
the weekend and open up to the upper westerlies as the low fills.
Our region will be under the influence of a high amplitude upper
ridge and surface high pressure. 500MB trough will be crossing the
West Coast Sunday and the Rockies Monday and Tuesday as our ridge
gets pinched east.

According to the 06Z GFS, Tropical system Matthew will be a powerful
hurricane making landfall on the NC coast Wednesday evening. This
track varies a little from day to day as yesterday the GFS had it
just a little farther east. Over the last 2 to 3 days this model has
been consistent in stating their would be some East Coast impact
from this system. The new 12Z GFS now has the track just slightly
farther east and still close enough to the western wall of
circulation for some affects to Outer Banks.  Still the timing for
passage of NC coast still Wed evening. The GFS has the wind from the
east for our area beginning Tuesday around the north end of the
circulation of Matthew.  The ECMWF is much slower with Matthew just
reaching the Bahamas at the end of the week. The end result for us
at this time is we will stay dry except for perhaps a few showers
late Wednesday north of CLT.

Temps a couple categories above normal Sunday through Tuesday then
Max Temps down near normal Wednesday due to passing Matthew.

&&

.AVIATION /02Z THURSDAY THROUGH MONDAY/...
At KCLT...a few lingering showers may move across the airfield this
evening, then drier conditions expected. The actual cold front, as
it were, does not appear to ever move across the region, or at least
there isn`t much of a wind shift behind it. In fact, the guidance
has the winds coming back around to a more southerly direction. The
guidance hits the fog hard again in the pre-dawn hours, with some
guidance going down as low as VLIFR. Will compromise and introduce
another MVFR fog restriction starting at 11Z. This could develop
earlier and could also be down in the LIFR or worse range, but those
details are left out for now. Any fog should burn off quickly. New
convection could blow up again across metro CLT by midday Thursday,
but this was left out for brevity.

Elsewhere...Drier air comes in this evening which should be enough
to keep clouds scattered. Over the mtns, looks like a good scenario
for valley fog in the pre-dawn hours, thus KAVL has a good chance to
see an IFR restriction, perhaps VLIFR by sunrise. KHKY has the next
best chance for seeing low stratus/fog based on its proximity to
trapped low level moisture near the front. Dry air is expected to
wrap around the mtns from the SW, so no fog is anticipated at the
Upstate TAF sites. Otherwise, VFR on Thursday after the fog burns
off. Showers are possible by early afternoon over the mtns, but this
was left out of KAVL for brevity.

Outlook: Dry high pressure will build in slowly behind the front
through Friday, which should bring VFR conditions in most places
through the end of the week.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     Med   63%     High  95%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  91%     High  91%     High 100%
KHKY       High  95%     High  90%     High  87%     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...DEO
NEAR TERM...PM/RWH
SHORT TERM...Wimberley
LONG TERM...DEO
AVIATION...RWH


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