Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 150632
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
232 AM EDT Fri Sep 15 2017

.SYNOPSIS...
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.  A more summer like pattern will highlight
the weather next week with diurnal rain chances and above normal
temperatures expected.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 225 AM EDT: The most immediate near-term concern early this
morning continues to be areas of fog and low stratus evident in the
IR difference imagery and in surface obs, mainly in the NC piedmont
and across the mountain river valleys. Model surface condensation
pressure deficits will be less than 5 mb throughout the forecast
area from 09Z to 12Z, and conditions will have to be monitored for a
possible Dense Fog Advisory. However, the mesoscale models do show
some slight dewpoint drying through daybreak as surface temperatures
fall, so perhaps the dense fog will be patchy enought in nature
across the piedmont/mountain valleys to handle with an SPS.

Otherwise, the main features in satellite imagery early this
morning include a trough axis extending southward from the Irma
remnants to the Carolina piedmont, a vorticity lobe moving ashore
along the central Gulf coast, and Hurricane Jose over the Atlantic
well east of the southeastern U.S. coastline. None of these feature
will impact the weather over the western Carolinas and northeast
Georgia today through tonight. The weak Gulf coast low will dampen
as it moves northeast into the shortwave ridge over the southern
Appalachians, and any associated moisture should remain suppressed
to the southwest. The HRRR does feature spotty mountain ridge top
showers this afternoon, and this is supported by weak wind field
convergence over the high terrain. Any sbCAPE this afternoon appears
quite limited, so no thunder is expected. The surface map will
feature 1018 mb high pressure overhead, but with a lingering, weak
lee trough through the piedmont. This surface high pressure will
gradually strengthen over the southern Appalachians through tonight.
Meanwhile, the axis of a weak upper jetlet should remain just
southeast of the forecast area to keep cirrus limited. This should
yield max temperatures today rebounding to around climatology in
most areas, with min temps a category above climo tonight.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 200 AM EDT Friday:  The short term fcst period kicks off on
Saturday morning amidst a rather significant shift in the synoptic
pattern as H5 ridging builds over the eastern CONUS, with troffing
out west.  At the surface, broad high pressure will stretch across
the Great Lakes into New England southward along the southern
Appalachians almost to the Gulf Coast.  Meanwhile, TC Jose remains
well offshore over the western Atlantic, with no land impacts
expected.  Pattern evolution through the period looks rather
uneventful as the upper anticyclone strengthens over the western
Gulf, with a few shallow weaknesses fcst in the height field both
Saturday and Sunday.  The surface pattern will remain consistent as
nely flow dominates thanks to the northern ridge, leading to drier
air advection across northeast GA and the western Carolinas.
Therefore, the fcst will remain dry as well, with the only exception
being over the mtns where minimal/sufficient cape is progged for a
few iso/sct showers each afternoon.  Temperatures through the period
will hover around normal.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 230 AM EDT Friday:  The medium range fcst period initializes
on Monday morning with upper ridging in control across the
southern/eastern CONUS, while troffing continues to prevail out
west.  At the surface the pattern will still be highlighted by
ridging along the Appalachians, however weakened a bit thanks to the
effects of TC Jose as it sweeps northward about 200 miles off the NC
coastline.  As the period evolves into Tuesday, Jose continues
moving northward and out of any effective range of northeast GA and
the western Carolinas, with it`s only impact being reinforcement of
drier nly flow.  The upper ridge by this time will have amplified
further as it gradually shifts eastward and overhead by Wednesday.
Meanwhile to the west, a series of shortwave impulses amongst the
longwave trof look to drive a surface front eastward into the MS
River late in the week, however with timing still to be determined
given model discontinuity.  This front looks to make a run at the
area sometime either Friday or Saturday, yet with some uncertainty
as it could also stall to the west given that the primary shortwave
looks to eject northeast over the Great Lakes.

As for the fcst across northeast GA and the Carolinas, pops remain
below climo through the period generally favoring a diurnal trend
with slight/chance levels over the high terrain, slight chances late
in the week over the foothills and western Piedmont regions, and dry
elsewhere.  Temperatures look to gradually moderate as the upper
ridge shifts eastward leading to near/above normal temperatures each
day.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
At KCLT and Elsewhere: Low stratus and fog are starting to develop
in some foothills and piedmont locations and across the mountain
river valleys early this morning. KAVL will certainly see periods of
LIFR visibility and low clouds, and IFR conditions will be quite
possible at KHKY as well. Slight dewpoint drying is indicated in the
numerical models this morning from KGSP to KCLT, but will hint at
low clouds with a FEW to SCT mention, while advertising mainly MVFR
visibility in fog through daybreak. The fog and low clouds should
scatter quickly through mid morning with mainly just FEW to SCT
cumulus developing with heating through the day. Any ridgetop
showers appear unlikely to impact KAVL at this point. Expect light
winds throughout, with more of a northerly component through the day
at the NC TAF sites, and some adjustment toward southerly winds at
the SC TAF sites by this afternoon.

Outlook: Isolated, mainly high terrain diurnal showers will continue
through the weekend into early next week. Morning mountain valley
fog/stratus are also possible each day.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       High  94%     High  97%     High 100%     High 100%
KGSP       High  83%     High  97%     High 100%     High 100%
KAVL       High  81%     High  90%     High 100%     High  85%
KHKY       Low   54%     High  97%     High 100%     High  97%
KGMU       High  97%     High  94%     High 100%     High 100%
KAND       High  97%     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...ARK/CDG/HG
NEAR TERM...HG
SHORT TERM...CDG
LONG TERM...CDG
AVIATION...HG



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