2025-2026 Fall/Winter Mountain Thread

[Maggie Valley Steve]

GSP stated in their afternoon disco that snow totals have increased again. I'll be watching the shorter term guidance the next 24 hours. I did see some of the convection allowing models suggesting up to a foot of snow along the highest peaks.

[nchighcountrywx]

Guidance for Thursday

[nchighcountrywx]

Official Guidance from NWS GSP:

 

Key message 2: Accumulating snowfall is expected to begin
Wednesday afternoon at high mountain elevations along the TN
border. Snow level falls over the mountains as temps cool through
the evening. Appreciable accumulations and the most significant
travel impacts still look to be confined to elevations above 3500
feet. Flurries cannot be ruled out Wed night or early Thu morning
in the Piedmont, though accumulation is not currently expected.

As noted in previous forecast cycles, a compact southern-stream
shortwave over the western Gulf Coast will phase with and be
absorbed by a substantially deeper shortwave associated with an
Arctic cold front tonight into early Wednesday. Low- to mid-level
flow will back and amplify over the CWA during this time, ahead of
the trough axis. Moisture return is limited at or below 850 mb,
though by Wed morning deep saturation is seen above 800-700 mb;
left-exit region of southern stream jet streak somewhat overlaps
with right-entrance region of the northern one to concurrently
bring some dynamic lift across GA and the Carolinas, which results
in light QPF response near our southeastern CWA border in some
models. This would be of little consequence given temps well above
freezing in those areas. Saturation occurs closer to the surface
during the afternoon just ahead of the surface front such that
mentionable PoPs develop over the mountains; RH will be high at ice
nucleation temperatures well aloft, so snow is possible wherever
temps are cold enough in the PBL. Only the highest peaks appear
likely to be cold enough for snow at onset, though rates greater
than an inch per hour appear possible there. CAA from around 21z
onward should begin to bring the snow level lower, particularly
considering the wet-bulb temp profile, though temps still don`t
cool fast enough to allow accumulation to begin in the valleys
until after 8 PM. Lift will be enhanced for a time as the base
of the shortwave shifts overhead, though drying quickly occurs
aloft behind that. However, with temps continuing to fall and
still decent low-level moisture, the PBL cools to support ice
nucleation near the surface, with the needed lift then mainly
resulting from NW upslope flow. Snow rates decline where NWF is
not a factor. With strong (near-advisory) winds/gusts continuing,
the upslope factor is respectable, and near 1"/hr rates look
to continue on the peaks until the low levels too dry out after
midnight Thu morning; additional accums after that time appear on
the order of an inch or less, even in the higher elevations.

Altogether it still appears this will be a highly elevation
dependent event. Event totals of 4 to 8 inches now are expected
in the highest elevations of the Smokies, with 3 to 6 inches
on some of the higher peaks in the northern mountains and near
Mt Mitchell. The larger cities in the mountain zones may not
even see an inch per the current forecast, and averages for the
lower-elevation portions of the zones are well below the 2 inch
threshold for Winter Wx Advisory. Hence no Advisory is being hoisted
at the current time, per local policy of considering the above-
and below-3500 ft averages. Avery is considered as one zone as
usual and does not meet the 2 inch criterion either. All this said,
even the light accums may lead to some travel issues given overnight
temps falling mostly into the teens, so will continue HWO mention.

For the Piedmont, 15-30% PoPs are warranted Wed evening ahead of the
base of the shortwave, though temps will be too warm for anything
but rain at that time. Most model depictions show the cold air
just barely chasing the precip, and particularly with saturation
aloft and wet-bulb profiles near freezing down to the surface,
it is reasonable to expect a few flurries will be seen. With the
late overnight onset of subfreezing sfc temps, however, and the
very light QPF depicted from those models producing it at all, any
accumulation looks unlikely. Did see fit to add a flurry mention
for the eastern I-85 and I-77 corridors where the overlap looks
most likely to occur.


Key message 3: Wind chills late Wed night and early Thu morning
could prove dangerous in some higher elevations, requiring adequate
protection from winter clothing.

As noted above, winds will be near Advisory criteria in higher
mountain elevations, where temps will fall into the lower teens
(upper single digits above zero above 5000 ft). Resultant apparent
temperatures fall into the -5 to -15 range which would support Cold
Weather Advisory. Confidence is moderately high for such conditions
above 3500 ft, but not yet confident if lower elevations may meet
criteria. There remains time for re-evaluation on tonight`s forecast
cycle, so will let the next shift take a look.


Key message 4: Significantly colder temperatures continue
Thursday through the weekend, albeit with a slight warmup on
Saturday. Dangerously cold wind chills will be possible above
3500 ft Saturday night and Sunday morning.

Any lingering light snow showers/flurries should end Thursday
morning as moisture dissipates. The bigger story will be a cold air
mass that moves in behind a departing cold front. Highs Thursday
will be much colder than Wednesday, as much as 15 to 20 degrees
below normal. Lows Thursday night will also be as much as 15 to 20
degrees below normal  With winds diminishing overnight, locations
with 5 below wind chill values should be limited to mainly locations
above 4000 feet.

Temperatures moderate Friday and Saturday high pressure moves east
and a southwesterly flow develops. Lows Friday night and highs
Saturday will range from near normal to up to 5 degrees below
normal. Highs Saturday will be near normal with steady for slightly
lower temps across the mountains.

Another cold front crosses the area late Saturday or Saturday night
bringing cold temperatures back into the region. Lows Saturday night
through Monday nights will be nearly steady 10 to 15 degrees below
normal. For now, winds appear to be low enough to keep wind chill
values out of advisory territory for all but the highest peaks.
Highs Sunday will be 15 to 20 degrees below normal then 5 to 10
degrees below normal Monday and Tuesday, with Monday the warmer of
the two days.


Key message 5: A clipper type low pressure/cold front may bring some
light snow to the mountains Friday night possibly into Sunday.

The cold air mass mentioned in the earlier key
message will be proceeded by a clipper type cold front. The
guidance varies greatly regarding this feature. The GFS favors a
double barreled system with light snow showers for the
mountains Friday night and early Saturday, then the second
system on Sunday. The Canadian has a stronger system Friday
night and Saturday with some precip spreading out of the
mountains, then a series of weaker systems through Tuesday for
mainly the NW flow precip areas. The ECMWF is similar to the GFS
for Friday night and Saturday then a weaker system on Monday
similar to the Canadian. And just to make things even more
uncertain, the Canadian and GFS have a different flavor of a
weaker font/clipper for Tuesday while the ECMWF is dry. The LREF
mean shows light precip Fri nite/Sat then again Sat nite/Sun.
The GEFS mean shows a light mountain event Fri nite/early Sat
then a stronger event Sun/Sun nite. The Canadian ensemble mean
shows a stronger event Fri nite/Sat with a weaker event Sat
nite/Sun. Obviously, this makes for a confusing and low
confidence forecast. As usual in these situations, have followed
the model blend which shows light snow potential for Fri nite
through Sat night with the possibility of some precip escaping
the mountains across the I-40 corridor Saturday. Stay tuned as
this will likely change.

[SEwakenosnowforu]

What are we looking at this weekend for two locations? Blowing rock Beeche mountain? What is the best day for the two? Saturday and Sunday.