Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 252032
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
432 PM EDT Sun Jun 25 2017

.SYNOPSIS...
Dry and cool air will continue to spread in from the northwest over
the forecast area through much of the week as Canadian high pressure
remains to our north. As the high moves offshore, moist southerly
flow will return toward the end of the week through the weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
420 PM update: A very broad trough covers the eastern two
thirds of the nation this afternoon. Weak impulses rounding the
trough continue to cross the southern Appalachians and adjacent
foothills/piedmont and residual moisture lingers mainly at mid
and high levels of the atmosphere. Some fairly thick clouds have
resulted at times, with even a few sprinkles falling from high-base
clouds. It no longer appears any of the small SBCAPE present on
the short-term model analyses will be tapped, so the chance of
accumulating showers has been dropped below slight-chance. However,
isolated sprinkles have been mentioned thru evening. Mid and high
clouds may linger for a while as a jetlet stretches from the OH
river valley to the New England through tomorrow. Lower level
moisture is uncertain overnight across NE GA and the lakelands of
the western Upstate after a day of drier weather. However, patchy
fog near rivers, lakes, and bodies of water will remain possible.
Mins will continue to fall into the 40s/50s mountains and upper
50s to lower 60s east.

A weakly reinforcing cold front, with little to no moisture, will
move through the region on Monday to bring in slightly cooler
and drier air. Maxes will be about a category below climo Monday
afternoon.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM EDT Sunday:  The short term fcst period kicks off
on Monday evening amidst broad H5 troffing across much of the
east/central CONUS, while a series of shortwave impulses pass
through the mean flow aloft.  At the surface,  a weak/dry cold front
will be making its way into/through the high terrain of western NC
as high pressure slides east across the TN Valley.  Given the drier
nature of this fropa as well as a lack of any sig shortwave energy,
will keep the fcst dry through the overnight hours.  However,
by early/mid Tuesday afternoon a slightly more potent shortwave
will accompany another reinforcing cold front, which will dive
through the OH valley into east TN/KY then western VA/WVA by
Tuesday evening.  Given improved convergence along the front as
well as weak upper forcing thanks to the shortwave, think convection
will be possible across the aforementioned areas, eventually moving
at/into western NC by late day Tuesday.  Therefore the fcst will
feature slight/chance pops across portions of western NC with the
highest pops being across the mtns along/north of I40.  Beyond that,
broad surface high pressure will consume the fcst area for Wednesday
leading to pleasant conditions.  Temperatures/dewpoints will be the
primary highlight of this fcst period as highs top out each day
nearly 6-8 degrees below normal, with dewpoints in the lower/mid
50s yielding low RH values.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 155 PM EDT Sunday: No sigfnt changes needed to the going fcst.
The models continue to show the transition from a unseasonal trof /
Canadian sfc high config into more of a normal summertime pattern.
There shud be enuf llvl moisture adv for mtn top convg shrs/tstms
Thu afternoon but coverage will be limited as upper heights rise and
a subtrop ridge noses in from the east. Things become more
interesting Fri thru the period as sfc-based instability increases
and easily breaks a weak cap each afternoon allowing for stronger
diurnal convection with better coverage...mainly across the higher
terrain Fri. Mid level LRs increase to arnd 6.5 C/km on Sat associated
with an incoming h5 s/w which will develop stg/svr activity over the
mtns/fthills spreading east across the piedmont regions thru the
late afternoon and evening. A cold front approaches the FA late Sat
and there is decent agreement in the guidance to suspect the front
will push into the FA and become quasi-stationary Sun. Thus...above
normal coverage will be had with thunder activity developing within
a continued unstable atmos. Max temp will begin the period a little
lower than normal and increase to near or just above normal by the
weekend. Mins will also rebound to normal levels in an increasingly
moist environ.

&&

.AVIATION /21Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Expect mainly mid and high cloud ceilings
through the period as an upper jetlet persists from the OH valley to
New England in the broad upper trough. A few sprinkles will be
possible. Patchy fog will be possible across the southwest
mountain river valleys and near the Upstate lakes, but much less
so than last night given the ongoing drying in northerly flow.
North winds less than 10 kt will continue through 18Z Monday,
except for some low end gusts at KAVL through late this
afternoon.

Outlook: Light winds and VFR conditions should continue through most
of the week. Return flow moisture will return around the offshore
ridge Thursday into Friday.

Confidence Table...

            20-02Z        02-08Z        08-14Z        14-18Z
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...SBK
NEAR TERM...HG/Wimberley
SHORT TERM...CDG
LONG TERM...SBK
AVIATION...HG


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