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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 271803
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
103 PM EST Sat Feb 27 2021

.SYNOPSIS...
A front stalled south of our region will gradually lift
northward as a warm front through Sunday. A cold front will approach
the southern Appalachians from the northwest Sunday night and cross
the area on Monday. Dry high pressure moves from the Great Lakes to
the mid Atlantic coast Monday night into Tuesday before unsettled
weather returns from the west Tuesday night into Wednesday. A
stronger storm system could arrive by Friday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 100 PM: The CWA remains under a decaying CAD setup, with
parent high already well off the East Coast and continuing to
distance itself from our area, and low-level winds veering such
that low-level upglide is pretty much history. That said, strong
inversion is expected to limit mixing, and cloud cover looks pretty
stubborn this aftn. Still retaining plentiful low clouds thru the
aftn, and brought max T values down. However, any insolation will
lead temps to rebound rapidly wherever breaks/scattering do occur;
warmest airport site in the CWA is Franklin with temp of 68; still
in the 40s at the sites where the low cigs have not managed to budge
at all. Think many of those areas will see enough lifting/scattering
to allow temps in the mid-50s at least by mid-aftn.

The sub-trop ridge becomes the dominant feature thru the rest of
the period as a warm/stat front develops just to the NW of the
area. Have maintained low-end chance PoPs across the NC mtns
this afternoon and thru the overnight within continued moist
mech lift; the previous fcst values from early morning still look
good. Pockets of h5 vort energy will traverse the aforementioned
frontal zone today and enhance the convective potential. By the
afternoon/evening general thunderstorms are possible along the nrn
TN/NC spine, with most of this activity developing on the TN side,
however, a couple tstms are possible across the nrn NC mtns as well.

With increasing llvl GOM moisture and stratus likely developing
overnight, expect mins to be held quite a bit abv normal with
readings generally in the 50s over most locales.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 230 am EST Saturday: Deep layer southwesterly flow will
continue over the southeastern U.S. on Sunday, with a split flow
pattern developing back over the western and central CONUS.
Meanwhile, deeper moisture will remain wrapped north and west of our
area through the day on Sunday along a stalled frontal boundary. The
southwest flow and associated warming of 850 mb temps will permit
maxes to run well into the 70s for many areas Sunday afternoon, with
PoPs for showers generally confined to northern and western
sections.

The more progressive northern stream will send shortwave energy into
the lower Ohio Valley Sunday night, while the southern stream
develops into a cutoff low over west Texas. The northern stream
trough will cross the southern Appalachians Monday and push a cold
front through the region. The deepest moisture and forcing ahead of
the sagging cold front will occur late Sunday night into Monday
morning, with drying from the northwest Monday afternoon. QPF
amounts are down slightly given the better forward movement of the
boundary on recent model runs. Instability with the fropa will be
modest as well, so neither hydro nor severe appear to be prominent
concerns - although a heavy rain mention will be continued in the
mountains in the HWO for very isolated, minor flooding late Sunday
night.

Right entrance region upper jet divergence will cross the area late
Monday post fropa, however, deep-layer drying will have developed by
then and dry profiles continue through Monday night in the
northwesterly flow. The only exception will be very shallow
northwest flow moisture in the NC mountains Monday night, but any
brief snow shower or snow flurry activity looks quite isolated at
best along the spine of the northern mountains.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
As of 230 am EST Saturday: Disparate solutions exist among the
models in the Tuesday timeframe with regards to the handling of the
southern stream low/trough evolution eastward from the southern
plains to the lower MS River Valley. The ECMWF has considerably more
forcing and associated moisture through mid week, with the GFS
drier. Will keep a chance PoP mention in the forecast for Tuesday
night and Wednesday at present during the best consensus period.
Given the strength of the high to the north, and chilly thicknesses
in place on Tuesday, there is some potential for mixed mountain/nrn
tier ptypes at onset Tuesday night.

The passing upper energy will move east of the area on Thursday,
with a relative lull in the forecast expected. The next robust
southern stream system may begin to approach the Deep South on
Friday. Anticipate moisture spilling back into the region from the
west ahead of this system Thursday night through Friday, but again
with considerable model uncertainty. Will focus the best chance PoPs
for showers on Friday.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Low stratus/stratocu deck associated with
decaying CAD regime will make for a tricky forecast this aftn
at all sites except KAVL. The initially widespread LIFR deck has
begun to scatter/lift in some spots but has remained essentially
unchanged since daybreak elsewhere. LAMP guidance is having trouble
keeping up with the trends, it seems. Have leaned pessimistic in
the first few hrs, but gradual improvement does look likely this
aftn across the SC sites and KCLT. Erosion of the deck should
allow VFR to persist into evening. A weak front will stall across
the area late today, being reactivated as a warm front tonight by
low pressure over the mid-MS Valley. Combined with a moist PBL,
that looks likely to bring back IFR-LIFR cigs and fog (possibly
dense) by early morning to most of the area. This likely won`t
scatter/lift until nearly midday Sunday. Winds will be fairly
light and mainly southwesterly today/tonight; gusts will develop
Sunday, especially following the erosion of the low clouds, with
deep mixing in the presence of fairly strong midlevel winds in the
warm sector of the aforementioned low. Precip chances are too low
to mention this period.

Outlook: Flight restrictions and chances for precip are expected
to return Sunday and linger into early next week. Drier hipres
will build back into the area by Tuesday.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High  83%     High  90%     Med   61%     Med   70%
KGSP       High  87%     High  95%     Med   75%     Med   78%
KAVL       Med   73%     High  96%     High  88%     High  95%
KHKY       Med   78%     Med   76%     Med   62%     Med   65%
KGMU       High  87%     High  95%     High  82%     High  80%
KAND       High  84%     High  95%     High  87%     High  86%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...DEO
NEAR TERM...SBK/Wimberley
SHORT TERM...HG
LONG TERM...HG
AVIATION...Wimberley