Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 142358

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
758 PM EDT Thu Sep 14 2017

The remnants of Irma exit to the northeast and dissipate through
tonight. Weak high pressure will build across the area Friday and
persist into early next week, keeping rain chances low. Hurricane
Jose is forecast to remain over the Atlantic and appears unlikely to
impact the Carolinas or Georgia.


As of 750 PM: Isolated to widely scattered showers continue to move
steadily E/NE along the I-40 corridor east of the Blue Ridge this
evening, but are expected to move east of the area and/or generally
dissipate by midnight. Mid clouds should gradually clear and lower
clouds scatter from west to east through the evening.

At long last, we finally rid ourselves of anything remotely related
to what is left of Irma tonight. Instead, by morning we end up under
a fast-moving confluent flow on the east side of a blocky-looking
upper pattern with a ridge over the Midwest and a weak trof along
the Gulf coast. Any waves get sheared apart, thus we have no
support for any precip late tonight or on Friday. Lingering low
level moisture could result in patchy dense fog in the mountain
valleys toward daybreak, and enough of that moisture remains east
of the mtns underneath dry air aloft to raise some concern for
patches of dense fog outside the mtns. Will have to monitor this
situation overnight. On Friday, we might be able to eke out a few
showers over the higher terrain, so a slight chance was kept over
parts of the Balsams and Black Mtns in the afternoon. Temps should
rebound close to normal with less cloud cover.


As of 2:30pm EDT Thursday:  Weather pattern will not change much
Saturday and Sunday with a broad upper high over the area.  588 dam
height contour over GSP Friday night is still there Sunday night,
with only a slight perturbation from TS Jose out in the Atlantic. A weak
area of surface high pressure will be over the area with a weak
easterly to northeasterly wind pattern that is slightly augmented by
Jose.  Impacts of Jose at this time look to be limited to some
slightly increased northeasterly to northerly winds Saturday and
Sunday, with moisture mostly remaining south and east of the
area.  Some very minimal CAPE around 300 j/kg in BUFKIT soundings
with very low-levels of windshear Saturday and Sunday afternoon give
an outside chance for a little thunder in the mountains, but most
areas will remain dry and mostly clear.  Temperatures will be just
above seasonal normal


As of 200 PM Thursday: Northerly confluent flow around the western
side of Hurricane Jose will anchor sfc high pressure over the CWFA
thru most of the medium range. An upper ridge will gradually build
in across the central, then eastern CONUS during the middle of next
week. This will allow temps to warm to slightly above normal with
continued dry conditions. Cannot rule out a few stray shallow
showers in the high terrain each AFTN, but forecast soundings show
fairly dry air and mid-level subsidence inversion keeping things dry.

Confidence in the forecast decreases by next Wed-Thu, as models
diverge on how amplified the upper flow gets. The ECMWF is more
amplified than the GFS in a deep trough in the west and ridge over
the Great Lakes. In either case, flow should start to turn out of
the east and perhaps south, allowing some moisture return atop the
CWFA. So PoPs increase slightly toward the end of the medium range,
as sfc high pressure axis begins to shift east. However, PoPs stay
below climo.


At KCLT and Elsewhere: Rain showers will pass in the vicinity of
KHKY and perhaps KCLT, warranting VCSH at those sites through
02-03Z. A brief visby restriction will be possible in the unlikely
event that a shower makes a direct hit on the terminal(s).
Otherwise, the main concern will be the potential for fog and/or low
stratus development later tonight, as mid-levels dry out while
moisture remains near the surface. The most likely locations for
restrictions (as usual), will be in the mtn valleys, and LIFR
conditions appear to be a good bet at KAVL by around 09Z-ish.
Restrictions also appear likely at KHKY, where the surface temp/dewp
spread was only 2 degrees at 23Z. Timing of restrictions there
remains uncertain, but a tempo for low-end MVFR is included btw
04-06Z, with categorical IFR/SCT003 by 07Z. Sub-MVFR conditions
appear less likely at the other terminals, but 3-5SM along with a
smattering of FEW/SCT IFR clouds is advertised at most of these
sites. Light SW winds will diminish through the evening, and
generally remain light/vrbl through the period. A few high terrain
showers are expected Fri afternoon, but expected sparse coverage
precludes a TAF mention attm.

Outlook: Isolated, mainly high terrain diurnal showers continue
into the weekend, with morning mountain valley fog/stratus also
possible. Some drying appears likely early next week.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       High 100%     High  88%     High  97%     High 100%
KGSP       High 100%     High  97%     High  97%     High 100%
KAVL       High  94%     High  84%     High  82%     High 100%
KHKY       High  97%     High  80%     High 100%     High 100%
KGMU       High 100%     High  97%     High  94%     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:




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