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000
FXUS62 KGSP 010718
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
218 AM EST Mon Mar 1 2021

.SYNOPSIS...
A cold front will cross the mountains early this morning and then
cross the foothills and Piedmont through the late morning and early
afternoon hours. Dry high pressure will build over from the north
tonight into Tuesday. Unsettled weather returns from the west
Tuesday night into Wednesday morning. Another low pressure system
may affect the Gulf Coast region Friday into Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 215 am EST: The latest surface analysis reveals a cold front
just west of the spine of the southern Appalachians early this
morning and beginning to make steadier forward progress. Ahead of
this boundary, gusty southwest winds have developed over the higher
terrain, but with max gusts likely staying just below advisory
values of 45 mph along the highest ridge tops. Precipitation will
begin to fill in quickly across the NC mountains as the frontal zone
and associated H5 vorticity reach the spine of the southern
Appalachians through the early morning hours, march on to the Blue
Ridge Mountains eastern escarpment by daybreak, then move east
across the foothills/Piedmont through late morning. The PoP trends
will follow this pattern, with categorical coverage likely at some
point for most locations, but with QPF values much better along the
TN border areas early this morning, and particularly across Graham
and Swain Counties in the best upslope flow and longest dwelling
period of the heavy rainfall. With QPF values around 1.5+ inches in
these areas, minor hydro problems could arise, but this should not
be sufficient for any widespread flooding and a Flash Flood Watch
does not appear to be needed. Instability remains quite marginal in
profiles. Will generally keep thunder out of the forecast, but an
isolated rumble cannot be completely ruled out with the fropa.

Temperature trends will be hard to pin down today, with falling
temps likely in the cold advection across the mountains, steady
temperatures across the northern tier in balanced cold advection but
warming post-fropa downslope flow, and a modest afternoon bump in
temps in the western Upstate and NE GA. Gusty northwest winds will
also develop in the cold advection through the day, but with gust
values again below advisory criteria in the windiest mountain
locations where a secondary, reinforcing cold fropa arrives this
afternooon. A trailing but vigorous shortwave will reach the
mountains again by late day. However, the deeper moisture should
settle generally southeast of our Piedmont counties by sundown along
with the passing cold front. Any shallow upslope moisture into the
western mountains will dry up fairly quickly in the cold air along
the spine of the mountains this evening. So, any isolated snow
showers or flurries will be short-lived and non-accumulating.
1032 mb surface high pressure will then build over the OH River
valley tonight, with chilly thicknesses spilling southward east of
the Appalachians.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 145 AM EST Monday...A split flow pattern aloft will evolve
into a general trof over the period as a srn stream h5 low traverses
the FA Tue night into Wed. A broad offshore sfc low will be
supported by this upper energy and will bring a decent amt of
GOM/Atl moisture to the area beginning Tue afternoon. Meanwhile, a cP
sfc high will track off the midAtl coast and provide a weak insitu
ridge before breaking down Wed morning.

This general pattern will likely support a wintry mix of precip
across the NC mtns Tue night, with light snow transitioning to
freezing rain, then to rain by 15z Wed. The latest NAM soundings
dropped across the NC escarpment show a strong and deep warm nose
interacting with sub-freezing sfc temps abv 3.5 Kft to support
-fzra, while the GFS is notably warmer with llvl partial thicknesses
and indicates more of a sn/ip situation. So, have blended the llvl
thermal profiles and used a top down approach for p/types, which
generated arnd an inch of snow across the higher peaks with perhaps
up to 2 inches over the Smokies. The freezing rain would begin arnd
08z and persist into mid morning with a few hundredths of an inch
favoring the nrn BR escarpment. If these ice amts hold over the next
few fcst cycles, an advisory may be issued. The atmos dries out
during the day Wed as a Canadian high drops south and reinforces a
srn stream sfc high building in from the west thru the period. Max
temps will remain a little below normal each day, while mins hover
arnd or a bit abv normal levels.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 210 AM EST Monday...The ext range fcst looks to remain quite
dry as the models continue to show a suppressed large-scale pattern
over the SE CONUS. Thus, little change was made to the already dry
fcst. A stg subs zone will slowly cross the area, while a couple cP
sfc highs build south and force a favored storm track well south of
the FA each day. With winds generally maintained n/ly and weak CAA
flow in place beginning Thu night, expect max temps to begin the
period Thu abv normal, then cool a little below normal Fri thru Sun.
Dewpoints will drop and mix out each afternoon, which could create
some fire-wx concerns across NE GA based on RH each afternoon,
except Sun when llvl moisture begins to return to the area. Winds
shud remain relatively weak, however, and plenty of sunshine will be
had making for rather nice days for early March.

&&

.AVIATION /07Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: Anticipate mainly thickening and lowering VFR
ceilings early this morning as a cold front and associated deeper
moisture moves in from the west. The narrow band of frontal moisture
should provide some MVFR to lower end VFR cigs during the passsage
of the main bands of rain showers with the front, generally from
just before daybreak west to mid-morning east. Returning VFR cigs
will then lift and scatter through the afternoon hours, with just
SCT high clouds tonight as drier high pressure builds in from the
north. Gusty southwest flow this morning will become slightly
gustier W to NW flow this afternoon following fropa and the onset of
cold advection. Most locations lose the gusts by early evening, but
KAVL will be the exception with continued NW gusts into the 20s
through 06Z Tuesday.

Outlook: VFR conditions briefly persist into Tuesday under dry high
pressure. However, moisture may surge back into the area by Tuesday
night, with restrictions and precipitation chances returning through
early Wednesday. Another round of drying is expected by late
Wednesday, likely continuing through the end of the work week.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High 100%     High  95%     High 100%     High 100%
KGSP       High  95%     High  91%     High 100%     High 100%
KAVL       High  83%     High  99%     High  99%     High 100%
KHKY       High  99%     High 100%     High 100%     High 100%
KGMU       High  95%     High  95%     High 100%     High 100%
KAND       High  96%     High  97%     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...HG
NEAR TERM...HG
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...HG