756
FXUS62 KGSP 101138
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
638 AM EST Fri Jan 10 2025

.SYNOPSIS...
A low pressure system brings a mix of wintry weather across the
entire area today into Saturday. High pressure returns by the end of
the weekend. Mostly dry conditions and cold air remains in place
through next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 635 AM Friday:

Key Messages:

1) Confidence is high that a winter storm will impact the area
this morning through early Saturday morning.

2) No significant change to previous thinking. Forecast appears to
still be on track. Latest model runs continue to show similar trends
in the precip type evolution and snow/ice amounts across the area.
significant increase in snow/ice amounts yet.

3) Regardless of precipitation type, the combination of storm total
snow, sleet and ice forecast supports the winter storm warning for
the entire area.

Morning update has the radar showing mainly virga moving into the
Lakelands at this time. Some very light precip may be reaching the
ground, but this is mainly setting the stage for eventual precip
arrival by moistening the lower levels of the atmosphere. Forecast
still generally on track with precip maybe starting an hour or so
earlier than previously expected. Temps are running a little warmer
than expected, but wet bulb temps are well below freezing across the
area, so temps will fall as precip moves in.

Otherwise, sprawling high pressure with arctic origins remains
entrenched across the region this evening with a cold and dry
airmass in place. Farther upstream, a southern stream trough
continues to dig across the Desert Southwest and northern Mexico as
intense Pacific jet energy dives down the Rockies. A northern stream
trough is also dropping across the Midwest and into the Great Lakes
region. Upper divergence overspreading a coastal baroclinic zone
draped along the Gulf Coast has instigated surface cyclogenesis
along the southeast Texas coast. The the surface low moves east
along the Gulf Coast today and lifts into far southern Georgia early
this evening then up the Carolina coast overnight. The guidance
still shows the upper systems not phasing, but there will still be
an increase in deep moisture and forcing. Precip moves into the area
after daybreak, spreads across the area through the day into the
evening, then moves out overnight, for all but the TN border
counties. The one potential caveat to all this is temps may warm
slightly above freezing for the CLT Metro where precip starts the
latest. Overall wet bulb temps are looking a little warmer than
previously expected. Still, where any warming does occur, temps
should wet bulb down below freezing with precip moving in with only
a small limit to accumulations.

Thermal profiles and surface wet bulbs continue to show precip will
generally be snow as it moves in from the west. Possibly with some
sleet as temps wet bulb down. A warm nose develops with a
strengthening low level jet by afternoon. This causes sleet to mix
in from the SW with a change over to all sleet to move north across
the area with mainly freezing rain developing near and south of I-
85. The snow/sleet mix continues across the mountains into the
southern foothills and Piedmont of NC and northern Upstate, with
freezing rain to the south. Mainly snow continues over the northern
mountains and I-40 corridor. As the low begins to pull away from the
area during the evening, the warm nose moves east with precip
changing back to snow across the mountains, with sleet and freezing
rain moving up the I-77 corridor and sleet/freezing rain along I-85
and mainly freezing rain to the south. These precip type trends
generally continue overnight as precip comes to an end from west to
east. Some change over back to light snow on the back end may occur
before ending. The northern mountains and foothills will likely see
mainly snow with some sleet mixing in at times. Precip should move
east by daybreak for all but the TN border counties where NW flow
snow remains.

The QPF forecast has remained nearly unchanged from the previous
forecast. Of course, the actual precip type trend will determine the
eventual snow, sleet, and ice totals. For now, with the expected
scenario, Have 2 to 6 inches of snow, with locally higher amounts
across the higher elevations, in the NC mountains and 2 to 4 inches
across the SC/GA mountains. Some of this, especially from the French
Broad valley west and south into the SC/GA mountains will be sleet.
Generally 1 to 4 inches along and north of I-85. Again, a
significant portion of this will be sleet closer to I-85 and mostly
snow for the I-40 corridor. Generally around an inch to a dusting
south of I-85 with sleet mixed in as well. Ice totals will be around
0.25 inches south of I-85 decreasing as one moves north and west
over the forecast area.

Regardless of location and precipitation type, impacts are expected
to be potentially significant. Multiple days of cold weather has
resulted in cold ground/road temperatures. Travel impacts will
quickly ramp up following precipitation onset and the amount of
sleet/ice expected could make travel quite difficult. Power outages
are also expected and could become widespread in some locations.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 150 AM Friday: Picking up on Saturday, the low pressure system
that dropped wintry precipitation across the CWA moves up the east
coast. With the trough to the north lifting offshore, NW flow
ensues. Lingering snow showers likely across the higher elevations
of the NC mountains through the afternoon. After the snow tapers
off, short term becomes quiet. Flow aloft becomes more westerly as a
weak ridge traverses across the area on Sunday. The main concern for
the weekend is for black ice in areas where frozen precipitation
doesn`t have a chance to evaporate from the roads and highways.
Overnight temps on Saturday look to be dipping into the teens across
the mountains and 20s elsewhere. Similar conditions for Sunday night
as well. Otherwise, dry conditions prevail and colder air remains in
place.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 200 AM Friday: Generally quiet conditions continue through the
extended period as a strong, cut-off low across the Midwest churns
toward the east coast. Guidance from long range models suggest a
fast moving and weak cold front. This could bring a brief shot at NW
flow snow by Monday night at the higher elevations, but confidence
is very low given the QPF response is minimal. Synoptic pattern
through the remainder of the period keeps the area in a mostly dry
pattern with no significant systems on the horizon. With a more
dominate NW pattern, cold air remains in place, keeping temperatures
below normal through the period. All in all, a quiet period with
cold temps and minimal precipitation.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Lower VFR clouds and virga are moving near
KAND early this morning but should remain south of the other
terminals. Conditions will deteriorate rapidly as precipitation
spreads west to east from mid morning through early afternoon. Most
terminals will likely see at least an initial period of light snow
as the precip starts, which will bring the ceiling down to MVFR.
After about a two hour period, more significant precip will work its
way to the ground, most likely staying mainly snow at KAVL and KHKY,
and a mix of snow and sleet at the Upstate terminals and KCLT. AS
this happens, the ceiling and vis will come down to IFR and LIFR. At
KCLT and the SC sites a changeover to FZRA is expected late in the
afternoon or early evening as warmer air moves in above the surface.
KAVL and KHKY may see sleet mix in by late afternoon. Light
southerly winds develop after daybreak then turn light NE during the
evening, with KAVL remaining SE.

Outlook: The precip should move out in the early morning hours
on Saturday. Dry weather returns thereafter and persists into
next week.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Winter Storm Warning until 7 AM EST Saturday for GAZ010-017-
     018-026-028-029.
NC...Winter Storm Warning until 7 AM EST Saturday for NCZ033-
     035>037-048>053-056>059-062>065-068>072-082-501>510.
SC...Winter Storm Warning until 7 AM EST Saturday for SCZ008>014-
     019-101>109.

&&

$$

SYNOPSIS...CP
NEAR TERM...RWH
SHORT TERM...CP
LONG TERM...CP
AVIATION...RWH