Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 222047
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
447 PM EDT Wed Mar 22 2017

.SYNOPSIS...
Cooler air returns to the region behind a departing cold front and
will linger through the end of the work week. A warm front will lift
north over the region over the weekend bringing increased chances
for widespread precipitation.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 445 PM EDT Wednesday:  High pressure continues to build in from
the north this afternoon, while low/mid level moisture advects
southward across the Midlands/LowCountry.  As for our area,
a few lingering mid clouds are evident on VisSat south of I85,
while high cirrus/cirrostratus prevails elsewhere.  Otherwise,
light/moderate nely flow dominates at the surface with a few low
end gusts occasionally affecting the Piedmont locales.  As for
the fcst, tweaked t/td and sky trends to align with recent obs
and left the remainder of the fcst as it was for this update.

Previous Discussion: As heights rise over the Southeast, surface high pressure
will move from the Great Lakes to the Mid-Atlantic region by
tomorrow morning. Low level cold advection will continue through
that time, as the high takes on a CAD configuration. However, while
warm advection will ramp up over the high during the day, it does so
without enough moisture for sustained cloud cover, much less precip.
Therefore it looks unlikely CAD will remain locked in for long.

With skies remaining only partly cloudy overnight, temps are
expected to dip a few degrees below normal. A light breeze
is progged to persist overnight which should minimize any
frost. However, the northwest NC Piedmont is still expected to
drop below freezing. The Freeze Warning issued by the previous
shift will be expanded to include Lincoln and   counties with the
3 PM package. Despite sunshine, max temps will be held down 6-9
degrees below normal tomorrow as the cold airmass remains in place.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 230 PM EDT Wednesday: The end of the week looks like it
will start out dry as a ridge of high pressure at the surface is
supported by an upper level ridge off to the west. Fair weather
will prevail as the high pressure ridge slowly breaks down Thursday
night and Friday. The upper ridge axis should cross overhead late in
the day. We start to see a return flow of moisture setting up late
Friday night and early Saturday once the high moves into a more
favorable spot and the next system organizes over the srn Plains
and migrates eastward. This could lead to the development of some
light precip near the SC/northeast GA Blue Ridge and adjacent higher
terrain of NC by daybreak on Saturday. Min temps will be close
to problematic...in the mid 30s in some spots...but this is over
the NC mtns and think if anything the fcst will trend warmer. The
trof to the west will continue to approach through Saturday, but
the main short wave should stay to our west through sunset. An
increasing moist southerly flow should allow for precip activity
to gradually expand from the Blue Ridge in the afternoon. Temps
will return above normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 220 PM EDT Wednesday: Per the latest global model guidance,
quite the upper air pattern shift is in the offing during the medium
range, from highly amplified/not-very-progressive late this week, to
less amplified and highly progressive during the first half of next
week, although mean ridging will remain in place along the East
Coast through much of the period. The result will be a very warm and
unsettled period for the western Carolinas and northeast GA.

This trend will begin very early in the medium range, as a weakening
upper low is expected to spin toward the Ohio Valley on Sunday, with
attendant cold front sweeping toward the Appalachians by the end of
the day. Pops ramp up to likely (west) to chance (east) by Sunday
afternoon. Although instability is forecast to be more than ample
for deep convection, shear profiles, while adequate for organized
convection do not necessarily scream "severe weather," esp
considering the overall forcing profiles associated with upper low
will be weakening with time and lifting north of the area. Still,
isolated severe weather will be possible.

A brief lull in precip chances may be seen Sunday night and early
Monday. However, pops will ramp up again by Monday night, as the
next wave (responsible for kicking out the initial upper low)
follows closely behind. This one is also expected to weaken/dampen
as it approaches the East Coast, so while pops return to the chance
range during Monday night/Tues, forcing will again be weak across
our area. Instability and shear parameters will again be adequate,
but not much to get too worked up over re: the severe convective
threat.

By Day 7, there is more divergence in the short wave details among
the global models, with the ECMWF brushing the area with precip
associated with yet another weakening short wave, while the GFS
dries everything out by early Wed. We have maintained a slight
chance across the mtns as a not to the ECMWF. Otherwise, temps will
be well (i.e., a sold 10 degrees) above climo through the period.

&&

.AVIATION /21Z WEDNESDAY THROUGH MONDAY/...
At KCLT and elsewhere: VFR. Dry high pressure will build in from
the north tonight, in a pattern similar to CAD. However, moisture
will be insufficient to produce precipitation, and low cloud
cover will be confined to SW NC and western Upstate SC. Thus,
only KAVL and KAND are fcst to have a cig, which is still at VFR
level. Winds will reflect the CAD-like regime, mainly staying in
the NE quadrant through tonight in the Piedmont, but eventually
favoring SE at KAVL. The Piedmont sites may see winds veer to near
due E by midday Thu.

Outlook: Low level moisture begins to return from the south
Thursday thru Friday, resulting in a gradual increase in shower
chances and low cigs into the weekend.

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...Freeze Warning from midnight tonight to 9 AM EDT Thursday for
     NCZ035>037-056-057-069-072-502-504-506.
SC...None.

&&

$$
SYNOPSIS...JPT
NEAR TERM...CDG/Wimberley
SHORT TERM...PM
LONG TERM...JDL
AVIATION...Wimberley



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