Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 230217
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1017 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 1015 PM EDT Wednesday:  Little change needed to the immediate
near term as mostly clear skies prevail regionwide, with the
exception of some patchy low stratus around the Lakelands region
of the Upstate.  That being said, guidance has trended slightly
warmer with min temps into tomorrow morning given modest nely winds
at the surface, as well as some thin cirrus aloft.  Given this
guidance as well as recent ob trends being a bit warmer than fcst,
opted to blend in latest SuperBlend which effectively raised min
temps around a degree across northeast GA, the SC Upstate, and the
lower NC Piedmont.  As for the I40 corridor, temperatures are still
expected to fall to at or just below levels as skies are clearest
atop these zones, therefore even with the updated blend, min temps
satisfy the current Freeze Warning.  Otherwise, tweaked td/wind
via latest ob trends and left the remainder of the fcst as it was.

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 /02Z THURSDAY THROUGH MONDAY/...
At KCLT and Elsewhere: VFR through the period as high pressure
builds into a short lived hybrid CAD configuration as the period
progresses.  Thus, given dry low/mid lvls, all tafs feature high
clouds amidst modest nely flow through the first half of the
fcst cycle.  Beyond that, the surface ridge is set to reposition
itself off the Delmarva shores which will lead to a gradual veering
trend of the sfc winds to the ese.  Therefore did favor such at
all sites on Thursday afternoon.  Lastly, llv moisture advection
looks to initiate around the same time from the southwest therefore
low vfr clouds looks possible at the SC sites before periods end.

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...

            02-08Z        08-14Z        14-20Z        20-00Z
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 until 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...CDG


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