Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 231728
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
128 PM EDT Sat Sep 23 2017

.SYNOPSIS...
Drier and stronger high pressure will continue to build through the
weekend and persist through at least the middle of next week. In the
meantime, Tropical Cyclones Jose and Maria will remain off the east
coast.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 10:45am EDT Saturday:  Update to increase temps a couple
degrees and adjust POPs per latest CAMs.  Model blends do not seem
to quite follow the diurnal warming we are seeing with the
temperature at GSP already topping 80 degrees.

General weather pattern makes only subtle changes the next 36 hours
with eastern CONUS upper ridge making a small amount of eastward
progress, and hurricane Maria moving closer to the North Carolina
Outer Banks.  For Upstate SC and surrounding areas, Maria will do
little more than slightly enhance the northeasterly surface flow on
Sunday.

Chances for precip. are mostly limited to the mountains of
Northeast GA and Western NC where a smidgen of CAPE with scarce
wind shear will be present from late this morning through the
afternoon.  CAMs consistently produce some weak convection in this
area, with brief strong updrafts.  Some chance for morning valley
ground fog will continue tomorrow, along with seasonally warm
temperatures 5 to 10 degrees above normal.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
As of 325 AM Saturday: Stagnant dry/unseasonably warm weather will
persist through the short term and into the medium range, as a
highly amplified upper ridge tightens its grip on the eastern Conus.
The air mass is expected to become drier and more stable early in
the week, as surface ridge strengthens with the upper anticyclone
gradually spilling east of the northern/central Appalachians, and the
surface gradient tightens in response to Tropical Cyclone Maria
moving north from the Bahamas. Thus, even the isolated diurnal
convection that is expected over portions of the high terrain today
is expected to be a thing of the past by early next week. Temps will
remain above climo, but moderated slightly from recent days by
northeast low level flow.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 330 AM Saturday: Upper ridging will persist along the East
Coast into the medium range, although model run-to-run consistency
is resulting in increasing confidence that a pattern change is on
the horizon, as a series of potent short wave troughs are depicted
breaking down the ridge late in the week. In the interim, the
seasonably dry and not-so-seasonably warm weather will persist into
at least mid-week, as large scale subsidence persists within the
axis of the upper ridge, but also on the west side of T.C. Maria.

A cold front associated with the introduction of large scale height
falls into the eastern Conus will likely impact the area within the
late Thursday through early Friday time frame. However, it`s looking
increasingly likely that this will be largely a dry front for the
forecast area, as the circulation around Maria maintains a dry NE
low level flow. Slight chance pops will be maintained for mainly the
far western mountains during the aforementioned time frame, although
even that may be on the generous side. By the end of the week, temps
should be much closer to normal, if not a bit cooler than climo, as
continental high pressure builds into the Southeast.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Weather pattern will remain mostly benign
under an upper ridge with steady and light northeasterly winds and
some afternoon cumulus clouds near FL050 today and tomorrow.  Some
convective showers may occur over the mountains this evening, but
are not expected to reach any of the TAF sites. Only source of
restrictions will be the chances for fog at KAVL.  TAF represents
persistence with what has been occurring the last couple days with
shallow nocturnal valley ground fog that burns off around 14Z.

Outlook: Precip chances will wane through the weekend and early next
week. With clear skies and calm conditions, fog and/or low stratus
are likely to return in the mtn valleys each of the next few
mornings.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     Med   75%     Low   39%
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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...JPT
NEAR TERM...WJM
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...WJM


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