Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 220550
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1250 AM EST Wed Nov 22 2017

.SYNOPSIS...
Moist southerly flow in the lower atmosphere will bring some small
chances for rain or drizzle until a weak cold front crosses our area
tonight.  A passing area of low pressure to our south may bring some
precipitation to the Midlands and Southern Upstate on Thanksgiving
Day. However, from Friday through early next week, dry high pressure
will dominate our weather.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1250 AM: Showers and deep moisture are moving east of the area
and will end soon early this morning. This sets the stage for low
clouds and/or fog to develop by daybreak.

Upper trough across the Great Lakes continues to gradually propagate
eastward tonight as it`s associated cold front will push through the
area overnight. With lingering clouds, do not expect much of a
temperature drop overnight, as have kept with low to mid 40`s for
much of the area, and slightly cooler across the mountains. After
daybreak, any fog development will begin to disperse as dry air
infiltrates into the area from high pressure building in from the
west. This feature along with a sfc low moving just offshore up the
Carolina coast, increased pressure gradient across the area will aid
in increased northerly winds (up to 10 kts) on Wednesday, with
higher gusts from gap winds possible. High temperatures will climb
into the low to mid 60`s in the afternoon hours, as the mountains
remain a bit cooler in the upper 40`s to 50`s.

&&

.SHORT TERM /TONIGHT THROUGH FRIDAY/...
As of 230 PM Tuesday: A split 500 mb trough will phase into a deeper
longwave over the Appalachians on Thanksgiving, allowing a cool and
dry high pressure to settle in from the NW. As the trough phases,
weak cyclogenesis is expected over the eastern Gulf. The low will
slowly cross the FL Peninsula Thursday thru Friday. The 12z GFS is
still the only model that throws a shallow layer of moisture up into
the southern edge of the CWFA. It keeps a small area of light QPF
just south of Greenwood/Abbeville counties, and even then, the
forecast soundings look too dry for measurable rain. So I will go
with a dry fcst for Thanksgiving. There may be some stratocu across
NE GA and the Upstate, at least thru the morning, but otherwise, it
should be mostly sunny. Temps will be about 10 degrees below normal
on Thanksgiving, then rebound to about 3-5 degrees below normal on
Friday.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
As of 100 PM EST Tue: The medium range fcst period kicks off on
Friday night amidst broad eastern CONUS troffing with a northern
stream wave digging across the upper Midwest, while ridging prevails
out west.  At the surface, the wave that we have been watching
evolve in the guidance for a few days now continues to track
offshore, and therefore yielding no sig impacts across northeast
GA and the western Carolinas.  Weakening high pressure across the
region will allow for a brief period of wly/swly backed surface
flow into/through Saturday before the aforementioned northern
stream wave and surface cold front move into the region in the
evening/overnight hours.  There remains some discontinuity with
regard to any frontal precip as the GFS favors enough upper support
tied to the wave to produce a quick burst of rain, possibly snow
at the highest elevations, while the ECMWF remains dry.  As such,
both of these guidance sources favor no residual nwfs behind the
front among the cold advection.  Therefore, will leave the fcst
dry through this time frame.  Moving along, caa will prevail on
Sunday as deep layer high pressure settles across much of the
southern Appalachians leading to dry conditions and below normal
temperatures into Tuesday.    At that point, the upper ridge begins
to shift east taking the surface component along with it, leading to
sly veered flow and thus waa.  This is all ahead of a late period
front moving across the Mississippi River valley into Wednesday,
which shouldn`t yield any affects on the cwfa through periods end.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and Elsewhere: A mix of restrictions exist across the area
as showers and deep moisture move east of the area. Expect some
variation of low clouds and/or fog to remain or redevelop early this
morning. MVFR is expected most locations with IFR likely at normally
more foggy sites. IFR possible elsewhere. Restrictions should burn
off shortly after daybreak with VFR through the rest of the period.
Light northerly wind early this morning picks up in speed and
becomes gusty across much of the area. Winds go NE and drop off
slightly in speed this evening.

Outlook: Expect VFR through the forecast period as dry/cool
conditions prevail.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       Med   65%     High  87%     High 100%     High 100%
KGSP       Med   67%     High  92%     High 100%     High 100%
KAVL       High  80%     High 100%     High 100%     High 100%
KHKY       Med   78%     High  94%     High 100%     High 100%
KGMU       Med   68%     High  92%     High 100%     High 100%
KAND       Med   65%     High  84%     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...RWH/SGL
SHORT TERM...ARK
LONG TERM...CDG
AVIATION...RWH



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