Area Forecast Discussion
Issued by NWS Greer, SC

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564
FXUS62 KGSP 261839
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
239 PM EDT Mon Jun 26 2017

.SYNOPSIS...
A weak upper level system will bring showers to the mountains and
portions of the foothills on Tuesday, but otherwise dry and cooler
weather continues through Wednesday.  Cool high pressure moves
off the east coast on Thursday with warm and moist air moving north
from the Gulf through next weekend. This brings back the daily
chance of afternoon and evening showers and thunderstorms.

&&

.NEAR TERM /THROUGH TUESDAY/...
A broad ulvl trof will dominate the pattern thru the period with a
Canadian sfc high beginning to build in this evening. Current obs
show little in the way of Cu outside the mtns and will expect mostly
dry conds with perhaps some isol -shra over the mtn spine counties

The upper trof will become a little more acute as an embedded s/w
dives across the base. The best model timing concensus has the wave
reaching the NC mtns right arnd daybreak. Upper div increases before
that and some showery activity is possible over the mtns before
sunrise. However...the best chance for showers will be aft sunrise
thru 18z-20z as the s/w crosses east. Not expecting much activity
outside the mtns...but the NW piedmont could see some isol coverage.
Due to the dry llvls and mixing airmass...sbCAPE will be hard to
come by thru the day. The best instability will be across the srn NC
mtns where a couple tstms are possible....yet these would be short
lived and rather shallow. With a sfc high building in behind the
upper energy...the afternoon will see lessening -shra coverage and
clearing skies. A lower sfc theta/e airmass builds in and this will
hold max temps a couple cats or so below normal...esp north.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 230 PM EDT Monday: The aforementioned upper level trough and
short wave feature will be exiting our forecast area (FA) Tuesday
night. Skies should clear as a subsidence pattern shifts into the
region and high pressure settles in.

The high will bring quiet weather conditions Wednesday, but it will
be on the move. By Wednesday night the high will be off the east
coast, and our flow will gradually start to turn to the south.

The suite of short term guidance remains insistent on allowing some
isentropic upglide to reach about the western half of our FA late
Wednesday night and Thursday morning.

As a result dewpoints will be on the rise, clouds increasing, and
small or chance POPS will be featured in the west, mainly Thursday
afternoon. Our eastern FA should stay dry Thursday. Meanwhile,
SBCapes in the west reach between 1000-1500 J/kg. There appears to
be enough evidence to add thunder in those areas where instability
levels will be on the rise.

Minimum temperatures Tuesday might be darn well comfortable, with
some 40s in the higher terrain, to the upper 50s and lower 60s in
various parts of the piedmont.

From that point forward, the model thermal pattern depicts a gradual
increase, which is noted by the MOS guidance. Therefore, our
temperature forecast will show and upward trend into Thursday.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 140 PM EDT Monday: A pattern change will be well underway
by Thursday night with surface high pressure located near Bermuda
going into the start of the weekend with low level southerly flow
developing and continuing for days.  A weak cold front slides south
from the Great Lakes then stalls out near or just north of our area
through the weekend. PM instability increases from not much at all
Thursday evening to around 1000 CAPE Friday evening to just less
than 1500 Sat evening to above 1500 CAPE Sunday evening.  The
greatest coverage of convection expected over the mountains being
closer to the front and better source of moisture and instability.
Coverage to the likely range for portions of the mountains during
the late day hours. Low chance of severe especially if sunshine
creates greater instability in localized areas. Although 925mb level
wind through most of this period will be SW, 850mb wind on Friday is
forecast to be SW then become mostly from the west into early next
week.

Max temps will gradually rise from about a category below normal
Friday to only a degree or two below on Monday. These max temps held
down a bit by cloud cover.  Min temps near normal Friday morning
then 2 to 5 degrees above normal into early next week.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: A fairly quiet TAF period all sites. High
pressure will continue to build in across the region and make for
dry low levels. An ulvl s/w crosses early Tue and will bring it/s
own moisture making for sct -shra across the mtns and VFR clouds
elsewhere as it crosses east thru 18z. Not anticipating a sigfnt
VSBY threat with llvl drying continuing and rather low crossover
temps over the mtn valleys. Winds will back w/ly this evening
non/mtns in response to lee troffing...however a general veering to
north or ne/ly is expected thereafter thru the remainder of the
period.

Outlook: Light winds and VFR conditions should continue through mid
week. Moist, SLY return flow will return around the offshore ridge
by Thursday.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
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...DEO
NEAR TERM...SBK
SHORT TERM...TS
LONG TERM...DEO
AVIATION...SBK



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