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000
FXUS62 KGSP 281454
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
954 AM EST Sun Feb 28 2021

.SYNOPSIS...
A warm front will lift northward across the region today. A cold
front will approach the southern Appalachians from the northwest
tonight and then cross the area on Monday. Dry high pressure will
build over from the north as the high center moves from the Great
Lakes to the Mid-Atlantic coast Monday night into Tuesday. Unsettled
weather returns from the west Tuesday night into Wednesday morning.
Another low pressure system may affect the southeast Friday into
Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 935 am: Dense fog became more widespread after sunrise, but
has since begun to improve again, although pockets linger across the
southern NC and eastern SC Piedmont. These should improve to above
1/4 mile by 11 am or so, but lingering reduced visby will likely
linger through the morning. A Special Weather Statement for dense
fog remains in effect for about another hour.

The forecast area will remain in a sw/ly flow regime this afternoon
and evening ahead of an approaching cold front. Good mixing will
enable low-end gusts with moderate gusts likely across the higher
mtn elevations persisting thru the overnight period. A look at theta
charts indicate weak isent lift ahead of the front coupled with
low-end available moisture. So, think the best relative chance of
light rainshowers will occur across the srn NC mtns and BR
escarpment in mech lift throughout the day. However, the latest
short term guidance depicts some modest instability...generally
500-1000 J/kg of sbCAPE developing over southern Piedmont areas, and
the convection-allowing models are beginning to respond with some
spotty showers...mainly across the eastern SC Piedmont this
afternoon. A slight chance pops has therefore been introduced
there.

The front will take it/s time reaching the NC mtns, likely aft 08z,
when stronger sfc forcing and a llvl jet begin to generate higher
precip rates over the wrn NC mtns. Not anticipating any hydro
threats thru the near term period, but the lingering rainfall into
the short range may create isol and minor flooding over the far srn
NC mtns, mainly in wrn Graham Co thru late morning Mon.

Widespread low stratus and fog is causing some consternation
regarding max temps today, especially in light of the fact that
lingering in-situ cool pool is at least partially responsible.
However, anomalously high thickness values will result in a rapid
warm up in areas that see thinning cloud cover, which should be
observed in most areas by afternoon. The forecast was cooled a bit
to around 70 closer to the Blue Ridge, but lower/mid 70s still
appear to be a good bet across much of the Piedmont, with even some
upper 70s likely across the lower SC Piedmont. The mountain valleys
will reach the u60s to arnd 70 F. Mins tonight will also remain well
abv normal with readings likely ranging from the l50s over the mtn
valleys to the u50s south of the I-85 corridor.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY/...
As of 235 am EST Sunday: A progressive northern stream trough will
cross the eastern U.S. on Monday, steadily pushing the passing
surface cold front south of the region through the day. Anticipate
mainly morning rainfall along the passing frontal zone, with
precipitation rates and coverage decreasing as the moisture exits
the lower Piedmont during the afternoon. Brief upslope showers could
also linger into the afternoon along the TN border counties, but
still anticipate that basins can handle the event without any
flooding of note, so no Flood Watches are expected at this time.
Temperature trends will be hard to pin down Monday with the fropa.
Expect falling mountains temperatures through the day there in the
post fropa cold advection, but with a modest Piedmont spike in
midday temps with downslope warming and drying east of the
mountains.

Deep-layer drying will continue from the northwest Monday night as
the surface boundary settles off to the south. A southern stream
closed upper low over the southern Plains Monday night will lift
eastward through the lower MS River Valley on Tuesday. Meanwhile,
surface high pressure moving from the Midwest to New England will
permit cooler and drier air to spill southward into the region on
Tuesday. Upglide moisture could begin to return to our region
through late Tuesday. As forcing and better moisture with the
southern stream system reach the southern Appalachians Tuesday
night, mixed precipitation types may develop over the mountains,
especially at onset of the steadier precipitation. Profiles over the
high terrain suggest that snow may develop along the ridges Tuesday
evening, with ptypes transitioning to more of a mixed bag overnight
into Wednesday morning. The forcing and moisture should move east of
the forecast area by early Wednesday as the associated surface low
passes through Midlands of SC toward the NC coast. An HWO mention
for the mixed ptypes could be needed for the NC mountains for
Tuesday night/Wed morning. Temps should rebound at least a category
on Wednesday afternoon with better insolation returning.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
As of 245 am EST Sunday: Deep-layer northwest flow and modestly
building heights will set up Wednesday night through Thursday ahead
of yet another southern tier closed low pressure system moving east
across Texas during the period. Temperatures will rebound again into
the 60s east of the mountain by Thursday afternoon.

The latest GFS solution has trended toward the ECMWF camp of opening
up the southern stream system across the lower MS River Valley and
Deep South and bringing more modest forcing through the southeast
Friday night. Recent runs of the GFS have trended drier with this
late week system, but will keep solid chance PoPs going in a nod to
the wetter, more consistent ECMWF solutions. The ECMWF 850 mb and
surface low center tracks would be interesting for northern tier
snow potential, but this remains a long way off so no HWO mention
will be made for now. Saturday will be the chilly day of the
extended forecast, but with other days within a category or so of
climatology.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
At KCLT: Isol pockets of dense fog will persist around KCLT this
morning as a shallow llvl ridge has held highly moist air near the
sfc. The terminal may not get affected directly with dense fog and
likely remain in the MVFR/IFR range, yet dense fog is briefly
possible arnd daybreak. By 16z, increasing winds and deeper mixing
commences, which will end any fg threat. Winds will remain locked in
sw/ly ahead of an approaching wrn bndry and the gusty conds will
reduce aft 22z-23z.

Elsewhere: KHKY will have the best chance of locking in dense fog
and VLIFR restrictions this morning as other sites remain a little
better mixed and will likely see VSBYs in the IFR range arnd
daybreak, except at KAVL where down-valley flow and lack of a
shallow inversion may keep conds in the VFR to MVFR range. Low-end
sw/ly gusts are likely this afternoon and will diminish after 23z.
KAVL will see the best chance of precip thru 06z with a moist
frontal bndry approaching the TN/NC line. Thus, a PROB30 with -shra
and possible IFR restrictions are mentioned aft 02z thru the
period.

Outlook: Periodic flight restrictions and chances for precip are
expected to linger Mon into Mon night. Drier high pressure will
build back into the area Tuesday.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       Med   75%     High 100%     High 100%     High  87%
KGSP       High  90%     High  98%     High 100%     High  87%
KAVL       High  85%     High 100%     High  98%     Med   63%
KHKY       High  85%     High  98%     High  95%     High  82%
KGMU       High  85%     High  98%     High 100%     High  89%
KAND       High  93%     High  95%     High 100%     High  82%

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...HG
NEAR TERM...JDL/SBK
SHORT TERM...HG
LONG TERM...HG
AVIATION...SBK