Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 260553
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
153 AM EDT FRI AUG 26 2016

.SYNOPSIS...
A weak surface front will settle southeast toward the region under
high pressure aloft through Friday. High pressure will rebuild over
the region through the weekend. A tropical low will gradually
strengthen off the southern tip of Florida early next week and then
possibly move toward the Gulf Coast through the week.

&&

.NEAR TERM /THROUGH TODAY/...
As of 150 AM: Restrictive fog and low clouds will be the primary
challenge overnight and early this morning. Based on forecast calm
winds and thin sky cover, NC mtn valleys should be the most likely
area to see fog this morning. I will forecast fog to develop near
KAVL by 10z, highlighting 10z to 13z for low ceilings. East of the
mtns, it appears that h925 winds will remain out of the NW and may
provide weak downslope winds across the foothills. KAND and KHKY
will be limited to patchy fog. KGSP and KGMU are expected to remain
clear. I will update the forecast to include the latest fog timing
and placement.

As of 1030 PM EDT Thursday:  Removed all pops on schedule as well
as removing any active wording from the HWO for the evening.  Took a
look at the latest temp guidance through the overnight and opted to
blend in the latest mav which effectively raised min temps around a
degree across much of the fcst area given continued mid/high cirrus.
Min temps will likely play a role in areal coverage of patchy
fog tonight, however it still looks as if the best chances once
again reside in the mtn valleys as well as the SC Lakelands region.
Furthermore, wouldn`t be suprised to see patchy fog across portions
of the NC fthills where xover temps are most critical.

Previous Discussion: An upper ridge was located over the southeast
this afternoon, and is expected to move little through Friday. The
models show moisture lingering over our area, with the best moisture
and instability over the Blue Ridge, especially on Friday.

Meanwhile, a weak surface boundary appears to drift south along the
Eastern Seaboard, causing winds to veer from southwest to northeast.
Temperatures will warm from slightly below normal to slightly
above normal.

&&

.SHORT TERM /TONIGHT THROUGH SUNDAY/...
As of 2 PM EDT Thursday: A 594 dm 500 mb ridge will remain centered
over the Mid-Atlantic region through the weekend. Low level flow
will be mainly easterly south of the mid level ridge axis. This
would seem to permit a very slow uptick in Atlantic moisture across
the western Carolinas, however backward parcel trajectories show a
more mid Appalachian source region for low level air arriving in the
mountains by Sunday. Thus, PoPs will be kept in the isolated to
scattered range for diurnal convection Saturday and Sunday
afternoons. Expect mainly an eastern mountain slope maximum, but
with a secondary maximum possible in weak piedmont surface troughing
and associated low level convergence. Warm mins will remain 8 to 10
degrees above climo, with maxes 4 to 8 above climo through the
weekend.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 230 PM EDT Thursday...the extended period picks up 00Z Monday
with an upper ridge over the southeastern CONUS. Though it is
flattening out by the time the medium range commences, its influence
over the local area will be maintained through the early part of
next week, resulting in precip chances below climo (and limited to
the higher terrain) and maximum temperatures about 5 degrees above
climo. Model guidance diverges at this point with the handling of
the ridge breakdown and the development of a potential tropical
system in the Bahamas, which lends a large amount of uncertainty to
the second half of the medium range forecast. No one global model
has show good consistency over the past 48 hours, so a clear
preference remains elusive and a multi-model blend was again used to
construct the forecast. A frontal boundary does appear to approach
the southern Appalachians by the middle of next week, which provides
a forcing mechanism for convection. If anything, guidance has
trended weaker and slower with the tropical system, with less
moisture transport into our area. Pops were ramped up to above climo
with little diurnal lull on Wednesday and Thursday to correspond
with the influence of the front and the possible influx of tropical
moisture, though a prolonged period of heavy rainfall does not
appear likely at this time.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
At KCLT: Sfc high pressure across the southeast U.S. will weaken
this afternoon, resulting in a weak trof to develop over the
east-central Carolinas this afternoon. The region will remain under
the center of a H594 dm ridge. This pattern should yield calm to
light winds, direction favoring the NE this morning to SE this
afternoon. Winds speeds should remain 6kts or less. Based on
forecast soundings, I will indicate the CU will remain FEW to SCT at
045 through the daylight hours.

Elsewhere: Restrictive fog and low clouds will be the primary
challenge overnight and early this morning. Based on forecast calm
winds and thin sky cover, KAVL should be the most likely terminal to
see fog this morning. I will forecast fog to develop near KAVL by
10z, then indicate a TEMPO from 10z to 13z for LIFR ceilings. East
of the mtns, it appears that h925 winds will remain out of the NW
and may provide weak downslope winds across the foothills. KAND and
KHKY will be limited to TEMPO mention for fog. KGSP and KGMU are
expected to remain VFR. Winds of 5kts or less will vary from SE to S
through much of the day. KAVL could see a VCTS between 20z to 0z.

Outlook: A deep ridge of high pressure will persist across the
region through early next week. The environment should support mid
to late afternoon thunderstorms each day, primarily over the mtns and
adjacent foothills. Weak steering flow should favor iso to sct
coverage, with storms dissipating with two hours following sunset.
Patchy fog will be possible any morning following a late afternoon
to early evening shower or thunderstorm.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High 100%     High 100%     High 100%     High  92%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Low   41%     High  85%     High 100%     High 100%
KHKY       High  80%     High  86%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High  94%     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...HG
NEAR TERM...NED
SHORT TERM...HG
LONG TERM...LEV
AVIATION...NED



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