301
FXUS64 KMRX 212325
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
625 PM EST Thu Nov 21 2024

...New AVIATION...

.SHORT TERM...
(This evening through Friday)
Issued at 248 PM EST Thu Nov 21 2024

Key Messages:

1. Breezy winds expected through Friday. Widespread gusts between 20-
35mph each afternoon. Higher elevations of the East Tennessee
mountains may encroach 40mph at times.

2. Snow showers are expected to bring 1-3 inches of snow to portions
of southwest Virginia and the East Tennessee mountains, with
isolated totals between 3-6 inches in the highest peaks and
ridgetops.

Discussion:

Snow:

Currently we have the first hints of winter weather moving
into our region with a couple of surface observations reporting snow
flurries in parts of southwest Virginia/northeast TN with the
isolated to scattered showers moving out of Kentucky towards the
southeast. This initial wave will move through this afternoon with
the primary effects likely to just be flurries in the sky as the
surface is probably not very susceptible to receive accumulating
snow with the recent sun and warmer temperatures, but some elevated
surfaces in the ridge lines of southwest VA could see a dusting by
the end of the day.

The main show when it comes to snowfall will come during the
overnight hours and into tomorrow morning. Expect more widespread
snowfall to move in a bit after 00z this evening from the northwest
as an area of enhanced energy/embedded low wraps around the south
side of the parent system which will be moving into the Mid Atlantic
overnight. This will result in a northwest flow event for our area.
This will be an extremely elevation based event with locations in
the valley staying warm enough that snow struggles to stick to the
ground, but in the mountain tops we could see over half a foot of
snow accumulate over the next couple of days. As higher resolution
models are getting a hold of this system the snowfall totals at the
tops of the mountains have increased compared to previous forecasts
as these help increase our confidence on the elevation aspect of
this event, which the longer range models don`t handle as well. Some
mountain and ridge tops in east TN and southwest VA do technically
reach above Winter Storm Warning criteria... However when you
average out the snowfall amounts in our counties we still look
likely to remain below warning criteria and more in line with a
Winter Weather Advisory. With that being said, we have added a
handful of counties in northeast TN and southwest VA to the
Advisory. All locations in Hawkins/Greene/Claiborn counties might
not get 1" of snow due to the warmer temperatures, BUT we expect the
heaviest snow to come just before the morning commute begins which
could cause driving issues. Expect some of the heavier snowfall to
accumulate in the 06-12z timeframe. So we`ve erred on the side of
caution and added some counties to the advisory where we think some
snow could accumulate on roads across the counties.

Additionally overnight we do expect to possibly hear of reports of
snow flurries as far south as Knoxville. However temperatures along
and south of Interstate 40 look to remain above freezing in the
Valley meaning that light snow that does occur this far south is
really going to struggle to stick to the ground.

As is typically with northwest flow events we could see light snow
continue for much of the day on Friday as moisture below 700mb
continues to get squeezed out along the mountains.

Winds/Wind Chills:

The other aspect of this system (which we`re already seeing outside
today) will be the continuation of the breezy conditions and
therefore low wind chill values. Similarly to the snowfall amounts,
the wind strength will also be highly elevation dependent with the
mountains and ridgetops seeing the breeziest conditions overnight,
possibly gusting up to 40 mph in the Appalachians. Given the
northwest nature however, HREF probabilities hold highest
probabilities of 40mph or greater(advisory criteria) to the eastern
slopes of the mountains so have continued to opt out of an advisory
at this time, as the mountain wave effect is going to occur on the
eastern side of the Appalachians. Breezy winds and cold temperatures
will combine for widespread wind chills in the 20s Thursday night
into Friday morning, with values into the single digits possible
across higher elevations.

&&

.LONG TERM...
(Friday night through next Thursday)
Issued at 248 PM EST Thu Nov 21 2024

Key Messages:

1. Very minor snow accumulations continue Friday night as northwest
flow continues.

2. Gusty winds continue Friday night through Saturday morning across
the higher elevations of the southern Appalachian Mountains. Gusts
from 30 to 40 mph will be common.

3. A return to normal temperatures by Sunday.

4. Rain returns to start the week.

Discussion:

Northwest flow snowfall continues across the area Friday night into
Saturday morning across the higher elevations of the east TN and
southwest VA mountains. However, only minor snowfall accumulations
are expected through this time as the moisture is drying up as the
upper low and trough push further east. Around 0.5 inches or less of
additional accumulation is expected.

Gusty winds continue across the southern Appalachian mountains
through Saturday morning. Wind gusts from 30 to 40 mph are expected
with the highest gusts on the tallest peaks. Then, winds begin to
decrease during the afternoon hours as the pressure gradient becomes
more lax. This is due to high pressure building in from the west and
the upper trough moving east.

Saturday and Sunday will be dry with high pressure over the
Southeast. Upper level flow will be zonal by Sunday. Saturday will
be a bit warmer with highs in the 50s for most of the Valley. Sunday
will be even warmer with highs around 60 in most Valley locations
and sunny skies.

The next system will move through Monday or Tuesday with weak
troughing at 500mb and a cold front at the surface. Temps will be
warm enough with this system for precip to be all rain. This looks
like a clean frontal passage with a slightly cooler, drier air mass
moving in on Tuesday. Another system will be possible later next
week but uncertainty is high.

&&

.AVIATION...
(00Z TAFS)
Issued at 602 PM EST Thu Nov 21 2024

Will see some snow showers and flurries mainly tonight, with the
highest chance of cigs/vsby lower than MVFR being at TRI later
tonight. At TYS, will take things no lower than MVFR overnight,
and expect VFR conditions for the entire period at CHA with very
little chance for any significant snow showers there. Winds will
be gusty from the west and northwest.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             36  50  37  57 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  35  47  38  54 /  30  10   0   0
Oak Ridge, TN                       34  47  37  54 /  20  10   0   0
Tri Cities Airport, TN              30  42  37  47 /  80  30  30   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Winter Weather Advisory until 10 AM EST Friday for Blount Smoky
     Mountains-Claiborne-Cocke Smoky Mountains-Hancock-Hawkins-
     Johnson-Northwest Carter-Northwest Greene-Sevier Smoky
     Mountains-Southeast Carter-Southeast Greene-Sullivan-Unicoi-
     Washington TN.

VA...Winter Weather Advisory until 10 AM EST Friday for Lee-Russell-
     Scott VA-Washington VA-Wise.

&&

$$

SHORT TERM...
LONG TERM....McD
AVIATION...