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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 271130
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
630 AM EST Sat Feb 27 2021

.SYNOPSIS...
A front stalled south of the region today 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 will build over from the north
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/...
-- Changed Discussion --
630 AM Update...The sfc wedge continues to weaken and become less
defined this morning. Not seeing any dense fog outside of the lower
NC mtn valleys, but there could be isol pockets of 1/2 SM or less
VSBY over the next few hrs mainly across the I-40 corridor. Low
clouds will hang tough and slowly lift thru the late morning.

400 AM Update...Isolated td/s are running a little lower than fcst/d
and have adj up in the grids. This leaves most locales with low
tdd/s, generally 0-3 F across the FA. The lowest vsby is occurring
along and north of I-40 and will continue to monitor this area for
possible dense fog formation as sfc wedge becomes more shallow thru
daybreak.

Low stCu and periods of light rain will continue across the FA this
morning and keep conds fairly steady state thru mid morning as a sfc
wedge begins to break down. Not anticipating a widespread dense fg
threat due to lack of rad cooling, but sfc tdd/s are running pretty
low across the nrn zones and will monitor thru for any possible
products, esp as the wedge weakens and lifts north arnd daybreak.

The sub-trop becomes the dominate feature thru the rest of the
period as a warm/stat front develops just to the NW of the area.
Will maintain low-end chance PoPs across the NC mtns this afternoon
and thru the overnight within continued moist mech lift. Pockets of
h5 vort energy will traverse the aforementioned frontal zone today
and enhance the convective potential. By the afternoon/evening
general thunderstorms look probable along the nrn TN/NC spine, with
most of this activity developing on the TN side, however, a few
tstms are possible across the nrn NC mtns as well.

Max temps will rebound today as the sfc flow becomes sw/ly
associated the strengthening sub-trop ridge and will expect highs
arnd 70 F over the srn zones and low to mid 60s north where cloud
cover will hang on longer. 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.
-- End Changed Discussion --

&&

.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 /12Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
At KCLT and elsewhere: Low-end flight cats will continue or develop
this morning across all TAF sites as a shallow sfc wedge begins to
weaken and moisture levels remain high. Expect KCLT to remain
IFR/LIFR thru late morning and introduced a TEMPO VLIFR aft 08z with
light rain affecting the area and likely lowering CIGs. Conds
improve slowly by the afternoon, with most sites going VFR, as
hipres works across the OH Valley and mixes in llvl dry air.
Northeasterly winds will switch to a sw/ly direction by mid morning
as the sfc wedge continues to breakdown and the synoptic pattern
favors an Atl ridge axis. A return of llvl moisture overnight will
generate IFR/LIFR CIGs aft 09z or so thru the morning hrs.

Outlook: Scattered to numerous showers with associated flight
restrictions are expected to return Sunday and linger into early
next week. Drier hipres will build back into the area by Tuesday.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High  89%     Med   75%     High  95%     High 100%
KGSP       High  89%     High  95%     High 100%     High 100%
KAVL       High  83%     High  80%     High 100%     High 100%
KHKY       High  83%     Med   75%     Med   75%     Med   66%
KGMU       High  89%     High  80%     Med   70%     High 100%
KAND       High  89%     High  80%     High  90%     High  94%

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
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...HG
NEAR TERM...SBK
SHORT TERM...HG
LONG TERM...HG
AVIATION...SBK