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424
FXUS62 KGSP 171424
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
924 AM EST Sat Nov 17 2018

.SYNOPSIS...
A gradual warming trend will develop over the weekend ahead of a
weak cold front approaching from the west. The front will move
through the area on Monday through Monday night, with moisture
mainly limited to the mountains. A dry, reinforcing cold front will
arrive from the northwest on Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
923 AM EST Update... Temperatures slow to rebound from widespread
lows in the 20s mountains to 30s piedmont so far this morning. Have
adjusted highs today a couple of degrees cooler to match
trends/latest guidance with highs today topping out in the 50s to
near 60. Any remaining valley fog should burn off in the next couple
of hours due to full sunshine.

A very nice near-term is in store for the fcst area. Upper level
flow remains nearly zonal and benign while a broad area of hipres
develops across the mid/Atl and ridges down the east coast. The
p/grad will remain loose which will keep winds weak and variable
generally ne/ly to se/ly. The latest NAM soundings show dry air thru
the column due to compressional warming with no good chance of Cu
development nor mlvl moist adv. So...expect mainly sunny skies with
passing streams of Ci. With steep inversions trapping llvl
moisture...there could be isol fg/fzfg issues this morning across
the mtn valleys, Upstate, NC piedmont...especially near larger
lakes. However, any fg that does develop shud be shallow and burn
off rather quickly after sunrise. Max temps will return to near
normal levels in very good insol while mins once again drop below
normal in very good rad cooling conds overnight which may lead to
another bout of patchy fg arnd daybreak.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 300 AM EST Saturday: Deep-layer WSW flow will continue over
the area on Sunday as weak surface high pressure persists over the
region. With southwesterly winds in the surface to 850 mb layer,
temperatures will continue to warm back toward climo values.

A broad eastern trough will start to carve out on Monday, with
associated surface reflections moving northeast along a frontal
boundary west of the Appalachians. Temperatures will finally rebound
to at or above climo in the continued warm advection. A narrow zone
of improving moisture will approach the spine of the southern
Appalachians late Monday to warrant isolated to scattered rain
shower chances there late Monday afternoon. A leading lobe of upper
vorticity will cross the region Monday night as the surface cold
front makes a push into and across the region. This boundary will be
accompanied mainly by westerly flow and a very narrow zone of
slightly deeper moisture. Any nighttime PoPs will probably be
confined to the western NC mountains. Post-fropa northwest flow
moisture early Tuesday morning may be able to wring out additional
light upslope precipitation. Profiles could support a mixover to
light freezing rain/drizzle along a few of the highest and colder
ridge tops, but ptypes will not be clear cut in this northwest flow
scenario where a little instability could also be present. At any
rate, wintry precipitation should not pose much of a threat in the
higher terrain, and conditions will remain dry east of the mountains
through daybreak Tuesday.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 315 AM EST Saturday: A trailing shortwave embedded in the
broad eastern trough will pass mainly north of the area on Tuesday.
Cold advection will kick in, but with some downslope warming,
especially over Upstate SC where maxes should remain in the lower
60s.

Wednesday will be the last day of good model agreement, with deep-
layer NW flow atop the area as heights begin to fall over the
southern plains. Dry surface high pressure will set up over the
Appalachians and then likely migrate to a more favorable damming
location over the northeast by Thursday. Temperatures will be one to
two categories cooler in the resulting thickness trough.

The GFS brings a southern stream wave eastward across the Gulf Coast
states on Thursday, while the ECWMF develops shortwave ridging from
the Appalachians westward. The discrepancies deepen on Friday as the
GFS maintains more zonal flow and the ECM camp features very
prominent height falls across the MS River Valley. Forecast
confidence will thus remain low for the late week holiday period.
There should at least be increasing clouds through Friday with a
southeasterly fetch likely bringing shallow Atlantic moisture back
to the Blue Ridge. In a slight nod to the ECMWF/NAEFS mean, will
feature Friday light rain PoPs in the slight chance range for now.

&&

.AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Surface hipres will continue to build across
the mid/Atl this morning and maintain a broad p/grad across all TAF
locations. A dry day will be on tap with no good chance of Cu or
mid/cloud development...mainly passing FEW/SCT Ci. Winds will remain
quite weak and VRB at times with a general ne/ly to se/ly direction
as the sfc high centers north of the area. Good rad cooling
overnight could lead to fg/br development at KCLT and most other TAF
sites by daybreak which will burn off by 13z/14z. A good coating of
frost is likely across all TAF sites this morning as frost points
have been reached at most locales.

Outlook: Gradually increasing potential for late night/early morning
mountain valley fog and near area lakes beginning early next week.
Otherwise, expect mostly VFR.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       High 100%     High 100%     High 100%     Med   75%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High  93%
KHKY       High 100%     High 100%     High 100%     Med   75%
KGMU       High 100%     High 100%     High 100%     High  93%
KAND       High 100%     High 100%     High 100%     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...HG
NEAR TERM...Munroe/SBK
SHORT TERM...HG
LONG TERM...HG
AVIATION...SBK