Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 150244
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1044 PM EDT Sat Oct 14 2017

.SYNOPSIS...
Drier and warm conditions will continue Sunday before a cold front
moves across the region Sunday night and 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 SUNDAY/...
As of 1030 PM EDT: The 00Z model runs are coming in with
low level condensation pressure deficit values of 3 to 6 mb
throughout the region for the pre-dawn hours, and this may well
indicate some overnight issues with dense fog. The main question
will be how much low stratus forms before visibilities can crash.
Certainly, boundary layer moisture persists and winds will be light,
so areas of fog seem likely. The fog could well become dense in some
locations, so this will need close monitoring for a possible Dense
Fog Advisory during the early morning hours.

Otherwise, large scale height falls will overspread the area by the
end of the near-term period, breaking down the Southeast ridge and
likely introducing a cold front into the southern Appalachians by
the end of the forecast period. Minimal instability is expected
across the area ahead of the cold front tomorrow afternoon. Thus,
any deep convection will hold off until the frontal circulation
impacts the area. This may occur prior to the end of the near term
period, so shower chances ranging from 20-50 percent are carried
across roughly the western third of the area by 00Z Monday. Temps
will remain about 10 degrees above climo through the period.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 230 PM Sat: A cold front will move into the mountains Sunday
night and then across the Piedmont on Monday morning. Expect
scattered showers ahead of the front. Instability will be very weak
so do not expect thunder. Rainfall amounts should be a quarter inch
or less.

The front will usher a cooler and much drier air mass into the
region. Once the cloudiness associated with the front clears the
area to the east Monday afternoon, expect clearing skies and
conditions that feel more like fall. Temperatures Monday night will
drop into the 30s in the mountains and 40s in the Piedmont. There
will be frost Monday night in some mountain locations under clear
skies and with light winds.

High pressure will be centered across the region on Tuesday leading
to mainly sunny skies and comfortable conditions with highs in the
50s and 60s.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 130 PM EDT Saturday:  The medium range fcst period kicks off
on Tuesday night amidst quasizonal ridging aloft across the eastern
CONUS, while a 1026mb high centered over the Delmarva dominates at
the surface.  Little/no change in the overall pattern is fcst
through Wednesday, while upper heights rise further as the ridge
amplifies on Thursday and Friday.  By that time the surface ridge
will have centered itself across the Southern Appalachians beneath
what looks to be a fairly broad ~590dm anticyclone.  While this
pattern persists through the remainder of the period across the
southeast, some amplification is evident late as an upper shortwave
moving through the Great Lakes drives a cold front into the MS and
lower OH valleys by Sunday morning.  Thus that will be something to
watch beyond the scope of this current fcst cycle, and in cycles to
come.  Otherwise, given the vast ridging described above, no
mentionable pops are featured through the period.  Temperatures look
to be the only sensible wx highlight as below normal levels are
featured Wednesday/Thursday, with a gradual warming trend expected
into/through the weekend thanks to the building upper high overhead
leading to a return to slightly above normal levels.  Regarding
those below normal temperatures on Wednesday, given the proximity of
the surface high during the predawn hours there is a decent chance
at some patchy frost in the mtns of western NC.

&&

.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: Patchy MVFR stratus/stratocumulus has already
developed in a few areas late this evening, and conditions will be a
race between lower stratus development and fog. Either way the good
radiation conditions of mostly clear skies and light winds early
will boost the chances for low stratus and IFR fog at the TAF sites
overnight. The forecast has trended more pessimistic in expectation
of this with a window of IFR to LIFR conditions centered around
daybreak. Expect light winds to pick up from the southwest through
the day tomorrow, with low clouds gradually scattering to VFR levels
by 15Z to 16Z. Any late day showers should remain west of a KAVL to
KAND line.

Outlook:  A cold front, with associated showers and restrictions,
will cross the region from the west Sunday night through early
Monday. Much drier and cooler air will filter in behind the front
and linger through the week.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     Med   73%     Med   76%     High 100%
KGSP       High 100%     Low   59%     High  80%     High 100%
KAVL       High  90%     Low   35%     High  86%     High 100%
KHKY       High  95%     Med   66%     High  81%     High 100%
KGMU       High 100%     Med   71%     Med   72%     High 100%
KAND       High 100%     Low   56%     Med   70%     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...SW
NEAR TERM...HG
SHORT TERM...SW
LONG TERM...CDG
AVIATION...HG



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