.DISCUSSION...
Issued at 1225 PM EST Thu Jan 22 2026
A significant winter storm is expected to impact the Southern
Appalachians and Tennessee Valley, and much of the south and central
CONUS, through the weekend. We are currently in a colder, longwave
troughing pattern across the Eastern CONUS with ridging across the
eastern Pacific. A northern stream shortwave will begin to phase
with an ejecting southern vort max on Sunday resulting in a quickly
intensifying surface low pressure system that will move northeast
across the East Coast.
Strong high pressure to the north keeps us dry today and Friday, but
increasing southerly flow aloft will result in increased cloud cover
late Friday into Saturday morning. As isentropic lift increases
across the region, light precipitation will be possible Saturday
morning, but dry air at the surface will limit any accumulating snow
or sleet. By the afternoon, the surface becomes saturated with
wintry precipitation expected to begin accumulating across the
region. To begin, areas near Interstate 40 and northward are
expected to have the entire atmospheric column below freezing which
will result in some potential snow to start on Saturday afternoon.
As southerly flow and WAA continues to warm temperatures between
850mb and 800mb, temperatures increase to around +2 to +3 degC by
late Saturday night and Sunday morning. This will result in a lot of
sleet and a transition to freezing rain across the region. In
addition, the southerly flow and subsidence along the western slopes
of the Appalachians will result in warming surface temperatures
across the western slopes of the mountains with areas around
Gatlinburg to Newport to Greeneville likely warming up above
freezing pretty quickly on Saturday night. This will limit ice
accumulation for these areas.
Across the valley and plateau, there are several variables that
will determine total snow, sleet, and freezing rain accumulation.
The first variable is the cold air aloft. Most of the snow will be
limited to areas near the Kentucky state line, and snow totals
will likely be compacted by sleet and freezing rain mixing in on
Saturday night. Further south, sleet and freezing rain will be the
predominant precipitation types on Saturday afternoon and night.
The second uncertain variable is the warm nose temperature around
800mb overnight; It will be near the sleet/freezing rain cutoff.
We likely get a mix of both sleet and freezing rain for much of
central East Tennessee, but depending on the exact mix, we may
have significantly more ice accretion due to freezing rain or
significantly more sleet (and less ice accretion). In addition,
the third variable is how cold are surface temperatures and where
do we wet bulb? Model guidance has significant variability in dew
points ahead of the precipitation, but based on the consensus of
most guidance, we should be cold enough in the mid 20s to get a
decent amount of ice accumulation before temperatures begin to
warm into Sunday morning.
Overall, a large portion of the region will likely see a trace to
a half-inch of sleet and one-quarter to one- half inch of ice
accumulation. Southern areas near the Georgia state line may only
see a trace to one-tenth of an inch of ice before the transition
to rain. The caveat across the south is the higher elevations
around Chattanooga such as Signal Mountain, Mowbray Mountain,
Lookout Mountain, and surrounding portions of the southern plateau
may see higher ice totals up to around 0.5 inch. Still, even
the lower amounts would cause significant travel impacts on
Saturday evening through Sunday morning. This forecast is likely
to change as we continue to refine the forecast with the most
recent observations tonight and tomorrow, so please continue to
follow the latest updates. Because of the uncertainty in
precipitation types and amounts, we will continue with the Winter
Storm Watch to message the risk of significant winter weather
hazards, and we will plan on upgrades to warnings or advisories
tonight or tomorrow when we are within 24 to 36 hours of the event
beginning.
On Sunday afternoon, the main 850mb low will be to our west with WAA
finally warming most, if not all, areas above freezing. Temperatures
will likely be slower to warm on Sunday morning across the valley
compared to what deterministic models indicate because of the cold,
dense air entrenched across the valley. WAA should finally win out
by the afternoon across the valley, but it will take some time. By
Sunday night, northwest flow returns with strong CAA and very cold
air arriving through the night and on Monday. We may continue to see
some orographic snowfall or rime ice across the northeast Tennessee
mountains through Monday morning, but accumulations should be light.
This very cold airmass will result in temperatures 20 to 25 degrees
below normal on Monday. Monday night into Tuesday morning,
temperatures drop down into the single digits for most locations
with temperatures near or below zero across the higher elevations.
Wind chill values across the higher terrain are forecast to be in
the -5F to -15F range; however, calm winds across the lower
elevations should mitigate the wind chill risk. Tuesday morning will
be frigid across the region, though.
As we move into mid-week, max temperatures begin to moderate but
remain 10 to 15 degrees below normal on Tuesday and Wednesday.
Another cold front will bring a reinforcing cold airmass by late
next week with temperatures struggling to get above freezing next
Thursday.
