Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 170735

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
335 AM EDT Tue Oct 17 2017

Dry conditions and below-normal temperatures will persist through
mid-week. Warmer temperatures will return later this week as
deep-layer ridging sets up over the southeastern states.


As of 300 AM: Ohio Valley high pressure maintains quiet weather
across the CWFA. Skies are clear across the area except for some
cirrus over the lower Piedmont, associated with a jet streak over
the SE Coastal Plain. This feature will drift further away from
the area this morning and should take the cirrus with it; clear
skies will persist through the day. Winds have tapered off at some
sites but breezes of a few knots continue here and there. Temps
are cool enough in the mtn and foothill valleys for patchy frost.

Expectations for today/tonight have not changed. Winds will remain
NE today, not bringing any downslope warming that may have been
at work yesterday. Thus max temps in the Piedmont are slightly
cooler. However, with full sun I still favored some component of
MOS to warm the blend a bit. The high builds east tonight which
reduces the gradient enough to calm winds in many areas. Mins
accordingly will be a bit cooler. Even favoring a dewpoint guidance
blend on the dry side of the spectrum, conditions appear favorable
for a more widely distributed frost event across sections of the NC
mountain counties, plus the northern foothills. Given the expected
coverage, a Frost Advisory is being issued for those areas, valid
tomorrow morning.


As of 135 AM EDT Tuesday: Weak upper trough slides east across the
area through the period. Surface high pressure remains in place
across the area as well. The air mass slowly moderates through the
period as thicknesses slowly rise. Highs slightly below normal
Wednesday rise to right around normal Thursday. Lows Wednesday night
will be 5 to 10 degrees below normal keeping frost potential in play
for the mountain valleys and I-40 corridor. Lows warm to a couple of
degrees below normal Thursday night ending widespread frost chance.


As of 330 AM EDT Tuesday: Guidance has been in good agreement
through Saturday. Now with the 00Z runs, the GFS and ECMWF are in
remarkable agreement through Monday. Upper ridge axis builds over
the area Friday and slides to the coast on Saturday. The center of
high pressure over the area Friday slides off shore Saturday with
some lingering ridging. This means a dry and warm forecast through
Saturday night but with increasing clouds late. Highs will be around
5 degrees above normal with lows starting a little below rising to
right around normal.

A full latitude trough will amplify over the central CONUS on
Sunday, before the southern stream cuts off near the Gulf Coast on
Monday. Although the low cuts off, it doesn`t happen until Monday
and retains some connection with the northern stream until then.
This keeps the low moving instead of stalling well to our west like
previous model runs were showing. At the surface, a moist southerly
flow develops between the departing high pressure and a cold front
moving into the MS Valley. The cold front moves into the area Monday
even as a surface wave forms near the Gulf Coast in response to the
developing upper low. This brings deep moisture into the area along
with good synoptic scale forcing resulting in increasing precip
chances Sunday and Monday. There is even enough instability for some
thunderstorms along and south of the I-85 corridor. Have capped PoP
in the good chance range for now. Highs remain near normal Sunday
falling below normal for Monday. Lows rise to nearly 10 degrees
above normal.


At KCLT and Elsewhere: VFR. Dry high pressure north of the region
will keep skies clear thru the period, save for some cirrus drifting
over the SC sites and KCLT early this morning. Winds will be mainly
NE. A few low-end gusts are likely in the late morning but these
should mix out quickly. Tonight, the center of the high nears,
and guidance suggests winds will become light and VRB.

Outlook: Seasonably cool and overall VFR conditions will persist
through the work week.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
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:


NC...Frost Advisory from 2 AM to 9 AM EDT Wednesday for NCZ033-


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