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000
FXUS62 KGSP 250005
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
705 PM EST Wed Feb 24 2021

.SYNOPSIS...
A relatively dry cold front crosses our region from the northwest
late tonight and Thursday, then stall to our south setting up an
active weather pattern through the weekend. Waves of low pressure
will cross from west to east into the start of next week.  Expect
dry high pressure to build over our area later next week.

&&

.NEAR TERM /THROUGH THURSDAY/...
As of 700 PM Wednesday: Gorgeous Wednesday across the area today,
with clear skies expected for the start of the nighttime period as
well. Near zonal flow aloft will keep thicknesses near the same
through tomorrow. A moisture starved cold front will enter the
region from the northwest tonight into Thursday morning. Enough
low-level moisture will be in store along the TN border to
activate precipitation development, mainly during the overnight
hours. However, that will stay confined to the TN border and will
likely remain dry elsewhere. Some cloud development will be in store
early Thursday over most locations in the cwa, but should gradually
dissipate after daybreak as dry CAA filters into the region, once
the front sweeps across the cwa around 12Z Thursday. This will
shift winds to come out of the N to NE by tomorrow afternoon as a
sfc high follows behind the frontal boundary and sets up shop over
the Midwest and OH Valley by the end of the period. The frontal
boundary should stall just south of the cwa as a shortwave trough
approaches the area from the west. No impacts are expect during
the near-term, but mid- to high-level clouds will begin to increase
by the end of the day Thursday. Temperatures will be slight above
normal tonight with increasing clouds and elevated dewpoints. Max
T`s will remain 5-10 degrees above normal, but will be a category
below what we saw today for highs.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 200PM Wednesday...we begin the short term with an essentially
zonal pattern across the southeastern U.S.  A 500mb shortwave trough
ejects out of the Four Corners region and tracks eastward through
the day on Friday.  Despite a distinct decrease in amplitude,
the trough remains visible in model output and should provide
ample QG forcing, with cloud cover ramping up Thursday night and
PoPs beginning to climb by the predawn hours Friday.  Meanwhile,
a strong high pressure system over the north Atlantic will begin
funneling cold, dry air into the Carolinas from the east, developing
a CAD-like wedge.  By Friday afternoon, strong, WAA-induced upglide
over this wedge should induce steady rainfall through the evening.
Frozen precip will be a concern Friday morning, as the dry surface
layer promotes wetbulbing.  Notably, this effect may continue to
drop surface temperatures even after sunrise as precip continues to
ramp up in the morning.  For now, looks like mainly wet snow, though
as WAA continues to strengthen the warm nose, some locations will
see a changeover to freezing rain in the late afternoon and evening.

Saturday may then see a lull in this activity, as good forcing
shifts eastward.  Dropped to chance PoPs into the end of the
short, as the warm front clears northward.  Weak surface CAA and
an eastward shift in the northeast high`s position should help
to erode the wedge Saturday, with the MSLP signature vanishing by
mid-afternoon.  Temps should consequently jump higher on Saturday,
perhaps into the mid/upper 50s.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 230PM EST Wednesday...a weakening 500mb trough moves offshore
Saturday night, while at the surface the now stalled frontal
boundary to our north continues to produce modest PoPs overnight.
A deep northern stream trough tracks out over the Great Lakes
from Canada, and by early Sunday will begin to push the stalled
frontal boundary southeast again.  Consequently, anticipating
another good chance for rainfall lasting through the day Monday,
before the frontal boundary passes us again as a cold front.
Highest QPFs still look to be in the SW Appalachians and Tennessee.

Still a good bit of uncertainty looking past this system.  The GFS
is trending drier, with high pressure taking hold beneath a broad
upper ridge.  The ECMWF and CMC both trend wetter, with a southern
stream shortwave promoting development of another surface low
impacting our CWA late Tuesday into Wednesday.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Expect VFR conditions to continue through
the period. Mid- to Upper-level clouds will be in store across all
TAF sites tonight and Thursday morning. Expect winds to come out
of the SW, but shift as a dry cold front passes through the area
by 12Z Thursday. Daytime heating and drier air filtering into the
region should allow for much of the clouds to dissipate during the
day. This will shift winds from the SW to the NW during the morning
hours and turn out of the N and NE by Thursday afternoon. Clouds
will begin to increase by the very end of the TAF period and could
be the start of some isolated flight restrictions.

Outlook: Deeper moisture returns late Thursday into early Friday
ahead of another storm system. Widespread precip and associated
flight restrictions are expected to develop on Friday and persist
into the weekend and possibly extending into early next week.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     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 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...CAC
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...CAC