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184
FXUS62 KGSP 191055
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
655 AM EDT Fri Oct 19 2018

.SYNOPSIS...
Cool high pressure will move off the east coast today as a cold
front approaches from the west. A narrow band of showers crosses our
region ahead of the front on Saturday. Much cooler and drier air
arrives behind the front Saturday night through Sunday. The dry and
cool air will linger into the early part of next week before the
weather becomes more unsettled by late week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 655 AM EDT Friday: Main update for the 12Z TAF issuance along
with minor tweaks to temperatures to coincide with latest trends, as
the rest of the near term forecast remains on track.

Otherwise, with sfc high pressure overhead, quiet conditions prevail
across the area this morning as light winds and nearly clear skies
allow for ideal radiational cooling to take place. As a result, low
cigs and patchy areas of fog have developed mainly across the
mountain valleys and into portions of the northern foothills as
well, and is expected to persist through daybreak. Temperatures have
dropped 10 to 15 degrees from yesterday`s high temperatures, with
latest obs depicting widespread low to upper 40s, into the 30s in
some mountain locations where patchy frost is possible.

Today, sfc high pressure will push offshore as latest guidance
continues to prog an eastward propagating upper trough pushing
through the Midwest later today/tonight.  After a day of sunshine
and high temperatures in the mid to upper 60s/near 70 degree, the
return of WSW flow will allow for increasing moisture across the
area. Thus, continue to anticipate the gradual infiltration of cloud
cover tonight ahead of the next approaching system. With available
forcing on the rise toward the end of the forecast period, isolated
showers will be possible, initially along the TN/NC border and
slowly expanding southeastward towards daybreak. With increased
cloud cover, overnight low temperatures will be nearly 5 to 10
degrees warmer than this morning.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 245 PM EDT Friday: A strong short wave dives into the OH
Valley Saturday creating height falls across our area. The short
wave passes by to our north Saturday night dragging a trough axis
across our area. At the surface, a cold front crosses the area
Saturday. There is a narrow band of deep moisture ahead of the front
the moves through rather quickly. The low level flow is also more
westerly limiting the inflow. Still, forcing is rather strong, so
have likely to high chance PoP across NC, falling to low chance or
slight chance across the Upstate and NE GA Saturday morning. Precip
chances drop of quickly during the afternoon as drier air moves in
behind the quickly moving front. Very little in the way of
instability, so thunder is not expected. The pattern favors NW flow
precip Saturday night with CAA, strong NW winds, and lingering low
level moisture. However, the moisture is not very deep, and the CAA
while strong, is not very cold. The moisture also diminishes quickly
after midnight. That said, the orographic lift could help the
moisture briefly reach the snow growth zone, so snow showers could
mix in across the higher elevations before ending. Winds could reach
advisory level across the NC Mountains Saturday night, but any
warning level gusts would be limited to locations above 5000 feet.
Winds will be gusty outside of the mountains as well. That said, the
Little TN Valley could be sheltered from the stronger winds. This
would limit frost potential to those valleys with a freeze possible
across the Northern Mountains and the higher elevations across the
Central and Southern Mountains.

High pressure and the colder air mass spreads across the area Sunday
and Sunday night. Clear skies and light winds will allow for good
radiational cooling conditions creating the threat of frost/freeze
conditions across much of the area.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 345 AM EDT Friday: Weak short waves cross the area Monday
night with low amplitude ridging moving in Tuesday through Thursday.
The cold air mass over the area Monday moderates before a dry cold
front moves through on Tuesday. Seasonal high pressure builds in
behind the front Wednesday and Thursday. The guidance then shows a
low pressure system moving east along the Gulf Coast Thursday. The
GFS is weaker and farther south with the low while the ECMWF is
stronger and farther north. As a result, the GFS is drier with much
less precip over our area while the ECMWF has much more moisture and
precip. Given the differences went with a model blend which has
slightly chance PoP Wednesday night and low end chance for Thursday.
Below normal temps Monday rise to just below normal for Tuesday and
Wednesday then fall back below normal on Thursday.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Areas of low cigs and patchy fog continues to
create IFR/LIFR at KHKY and KAVL this morning. Otherwise, VFR
prevails at the other terminals with nearly clear skies and light
winds. Expect flight restrictions at KHKY and KAVL to persist
through daybreak, if not an hour after. After daybreak, expect
conditions to improve to VFR at all sites with SE winds becoming
SW ahead of the next approaching cold front. Have kept with the
inherited trend of gradually increasing clouds late this
afternoon/tonight as chances for VCSH/-SHRA begins late tonight
across the TN/NC border, gradually expanding southeastward
across the FA through the end of the valid TAF period.

Outlook: A cold front passage Saturday will likely bring widespread
rain with associated restrictions. Improving conditions are expected
late Saturday into Sunday with breezy northwest winds behind the
front.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Med   69%     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...None.
SC...None.

&&

$$
SYNOPSIS...RWH
NEAR TERM...SGL
SHORT TERM...RWH
LONG TERM...RWH
AVIATION...SGL