Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 251756

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

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.


As of 145 pm EDT: 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 nearby areas 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. The sprinkles
should pass pretty quickly with the passing upper wave through late
afternoon, but the 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 will be much more questionable
tonight 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


As of 250 AM EDT Sunday: the short-term fcst picks up at 12z on
Monday with longwave upper trofing centered over the Great Lakes
and steep upper ridging in place over the Western CONUS. By early
Tuesday, an upper shortwave will dig southward on the backside
of the upper trof, providing increased upper-lvl divergence just
ahead of it. The shortwave axis is expected to move overhead Tues
afternoon and then offshore by early Wed with heights beginning
to recover in its wake. At the sfc, a lingering frontal bndy will
be located over the SC Coast early Monday and slowly drift offshore
later in the day/evening. The rest of the period is marked by the
Canadian High sliding SE and towards our area on Tuesday before
ending up just to our north by the end of the period, 12z Wed.
As for the sensible fcst, most of the period should be dry. I do
have some slight chance PoPs on Tues as the upper shortwave
approaches the area and produces favorable ascent especially over
the higher terrain. Temps will be 1 to 2 categories below normal
for late June.


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.


At KCLT and elsewhere: Expect mainly mid and high cloud ceilings
through the period as an upper jetlet persist from the OH valley to
New England in the broad upper trough. A few sprinkles will be
possible from the high based stratocumulus over the southwest
mountains, but with less chance east of the mountains through late
afternoon. 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...

            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:




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