Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 132330
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
730 PM EDT Fri Oct 13 2017

.SYNOPSIS...
Drier and warmer conditions return over the weekend before a
more robust cold front approaches the Carolinas Sunday night,
bringing a chance of showers to the area Monday. Considerably cooler
and drier air will spread over the region in the front`s wake and
linger through most of the next work week.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 720 PM EDT: Lowering stratus is filling in across the
region this evening as drier air continues to set up aloft atop the
very moist boundary layer, and as winds become light. With this
update, drizzle chances have been pared back toward the eastern
slopes of the mountains and immediately adjacent foothills. Areas of
fog still look quite likely overnight given model RH profiles, but
it remains too early to determine where dense fog will develop.
Condensation pressure deficits from 09Z to 12Z look lowest over the
mountains and along the I-40 corridor, but cannot rule out patchy
dense fog just about anywhere toward daybreak.

Otherwise, the upper ridge will remain in place over the Southeast
through the period, with low level thickness values well above
climatology. The moist surface ridge associated with hybrid cold air
damming will weaken through the period, as parent high pressure
moves well off the northeast Conus coast. Extensive cloud cover and
the high thickness values will result in min temps at least 10
degrees above climo overnight. With nothing to lock it into place,
cloud cover should gradually erode through mid to late Saturday
morning, giving way to a mostly sunny afternoon. This will allow max
temps to rebound to well above today`s values (and above
climatology).

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
As of 230 PM Friday: the short range period looks transitional,
almost like a change of seasons early next week. Expect that
any lingering cold air damming effects will have ended Saturday
evening as a chunk of the parent high breaks off and sits over the
Carolinas. Although the upper ridge will slide eastward overnight
and Sunday morning, it will continue to support surface high
pressure that should keep us fairly quiet, with the deeper moisture
and mid/upper forcing still off to the west. Temps on Sunday will
climb back almost ten degrees above normal again. The approach of
the upper trof/cold front from the west may be felt over the mtns
by the late afternoon, with shower chances ramping up as some weak
instability creeps in. The guidance is in fairly good agreement
with bringing the front across the fcst area Sunday night and early
Monday, so we ramp the precip chances up into the chance range from
the west in the overnight period. The models show this to be more
of an anafront case, so precip chances should linger behind the
front into the afternoon east of I-85, even as the front moves
off the coast. The cloud cover and scattered precip behind the
front will bring temps back down ten degrees or so, and back below
normal. On Monday night, high pressure will begin to build in from
the west and we should dry out and cool down dramatically. The fcst
as currently constructed brings low temps down well into the 30s,
and well into the frost range, over the NC mountains by daybreak
Tuesday. We anticipate the possibility of frost in some spots,
depending on how much the wind will calm in the pre-dawn hours.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 130 PM EDT Friday:  The medium range fcst period kicks off on
Tuesday morning amidst the passage of a cold front leading to a
developing caa regime as a deep upper trof slides east and a large
sfc ridge settles across the OH/TN valleys beneath a region of upper
subsidence.  Pattern evolution through the period will feature
continued deep layer ridging, strengthening into weeks end as the
upper pattern amplifies thanks to troffing out west.  Closer to home
this will lead to a period of more fall like conditions with below
normal temperatures and dry weather expected.  The only real
negative highlights of the period will be the possibility of frost
across portions of the NC mtns/fthills Tuesday morning, with
improved chances on Wednesday morning as the high settles overhead
yielding little overnight flow and good radiational cooling
conditions.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: Any ceiling improvement through the lower end
of MVFR has ended with sundown, and a steady transition down through
the IFR range is expected overnight, with periods of LIFR cigs
possible around daybreak. With less surface wind and mixing, and
drier air aloft, IFR visibility in fog also appears a better bet at
times overnight, with LIFR to VLIFR possible in mountain valley fog.
A slow recovery through MVFR is expected through mid to late
Saturday morning, but with scattered clouds and VFR conditions
likely for the afternoon in most areas. Expect light and variable
winds to become more light SE to S through Saturday in most
locations.

Outlook: Drier air should result in less chances of restrictions
Sunday, although mtn valley fog/low stratus will be possible once
again in the morning. A cold front, with associated showers and
restrictions, will cross the region from the west early next week,
with much drier and cooler air filtering in behind the front through
mid-week.

Confidence Table...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High  89%     Med   68%     Med   65%     Med   69%
KGSP       High  94%     Low   48%     High  80%     Med   75%
KAVL       High 100%     Med   73%     Low   46%     High 100%
KHKY       High 100%     Low   58%     Low   53%     Med   75%
KGMU       High  94%     Low   48%     High  80%     Med   75%
KAND       High  89%     Low   53%     Med   70%     Med   75%

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...JMP
NEAR TERM...HG
SHORT TERM...PM
LONG TERM...CDG
AVIATION...HG



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