021
FXUS64 KMRX 221752
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1252 PM EST Fri Nov 22 2024

...New AVIATION...

.UPDATE...
Issued at 1026 AM EST Fri Nov 22 2024

The Winter Weather Advisory set to expire at 10 AM EST this
morning, was allowed to expire. However, the Winter Weather
Advisory through 7 AM EST Saturday is still in effect for
isolated 2 to 4 inches of additional snow accumulation this
evening across the highest elevations of the Southern Appalachians
and southwest Virginia.

Many reports received of a half inch to the 2 inch range of
snowfall accumulation across much of the advisory area, but
places such as Roan Mountain and Mount LeConte saw anywhere
between 4 to 5 inches of snow. Snow has tapered for the most part
for now, and cloud breaks are allowing some sunshine. We expect
cloud cover to return, as well as another round of moisture this
evening and overnight, hence the Winter Weather Advisory for
additional accumulation for parts of the Southern Appalachians
mountain zones and the counties of Wise, Russell, and Washington
in southwest Virginia.

KS

&&

.SHORT TERM...
(Today and tonight)
Issued at 240 AM EST Fri Nov 22 2024

Key Messages:

1. Breezy winds expected today. Widespread gusts between 20-30
mph in the afternoon. Higher elevations of the East Tennessee
mountains may approach 40 mph at times.

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

Discussion:

Not much has changed in the forecast thinking in the past 12
hours. As expected, we are currently in the period heaviest
snowfall, associated with a trough axis rotating around the closed
low over the Mid Atlantic region. Cold temperatures aloft under
this trough will continue to produce widespread snow showers in
the northern half of the area through 12Z. Accumulations through
sunrise will be mainly in SW VA and the mountains where
temperatures are at or below freezing.

During the day, the trough moves to our east and dry air aloft
builds in, cutting off moisture above -10C. Upslope NW winds will
keep a chance of light snow accumulations in the mountains through
the day, but the wind speeds at 850 mb drop to around 20 kt.
Boundary layer mixing and downslope winds off the Plateau will
create some partial clearing of clouds in some Valley locations
this afternoon.

A second surge of snow showers is expected to arrive late this
afternoon and evening as we get an increase in 850 mb wind speeds
to around 40 kt in association with an upper jet streak rounding
the western side of the closed low. Moisture depth increases
slightly with saturation near 10C, so additional light
accumulations are likely from ~21Z to ~06Z. Temperatures during
this time will support an additional 1-3 inches of accumulation in
the mountains of SW VA and NE TN during this period.

Forecast snow amounts have not changed significantly with this
forecast package. However, with the expected round of additional
snow accumulation this evening, the Winter Weather Advisory will
be extended through tonight for the mountains and parts of SW VA.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 240 AM EST Fri Nov 22 2024

Key Messages:

1. Snow ends Saturday morning as northwest flow winds down. Gusty
winds decrease in the morning across higher elevations of the
southern Appalachian Mountains. Gusts of 30 mph still possible
through late Saturday morning northeast Tennessee mountains.

2. A return to above normal temperatures for late November on Sunday.

3. Rain returns Monday afternoon and night to start the week.

4. More significant system moves in late Wednesday and through
Thanksgiving. One to two inches of rain possible with this system.

Discussion:

Northwest flow snowfall continues across the extreme northeast into
Saturday morning across higher elevations of the southwest VA
mountains. Only trace amounts possible, mostly flurries into mid to
late morning as the moisture dries up with upper low and trough
moving east. The gusty winds should decrease over the higher
elevations of northeast Tennessee and southwest Virginia during the
late morning as the pressure gradient decreases.

High pressure builds in from the west Saturday as the upper trough
shifts east. Clouds will linger most of the day across northeast
Tennessee and southwest Virginia but become sunny over the central
and southern sections of east Tennessee and southwest North Carolina
by afternoon. Temperatures will range from 50s lower elevations
central and southern valley in the sunshine to 40s northeast and
higher elevations, except 30s highest elevations where clouds linger.

The coldest night of the week will be Sunday morning with lighter
winds and cold airmass. Lows mostly upper 20s to lower 30s except
mid 30s extreme south and southwest. Sunday even more warming as
surface high shifts quickly eastward in a almost zonal flow aloft.
Highs reach mid to upper 50s northeast to lower 60s central and
south to mid 60s at Chattanooga.

The next system will quickly approach and move through later Monday
into Tuesday afternoon. This system looks weak in the mid levels and
cold front produces only light rain of about 0.10 to 0.20 inches at
the surface. Temperatures are warm enough for the precipitation to
be all rain. A somewhat cooler and  drier air mass moves in Tuesday.

The next system will move into the region later Wednesday and
through Thanksgiving. This system looks much stronger than the
Monday system but the timing and development of the system is still
uncertain. Rainfall amounts are expected to be over 1 inch to around
2 inches and more significant colder air moving in behind it Friday.
Stay tuned as the evolution of the system may change in the coming
days.

&&

.AVIATION...
(18Z TAFS)
Issued at 1238 PM EST Fri Nov 22 2024

W-NWly winds will prevail, with gusts at times through the
afternoon at all terminals. TRI will experience the most
persistent and strongest gusts up to 25KT lasting overnight. CIGS
should remain VFR at CHA, but CIGS forecast to dip to MVFR at TYS
tonight and persist for the next several hours. VFR CIGS return
towards end of the TAF period. Though moisture is set to return,
not looking at great chances around TYS. TRI is forecast to reach
MVFR CIGS earlier than TYS and may dip into the lower end of MVFR
close to 1kft. Snow showers will return at TRI during the
overnight hours when another round of moisture swings down from
the NW. PROB30 added to reflect this due to possible non-
persistent showers. Snow showers should taper around/after 12z
leading to decreased winds and eventual return to VFR conditions
either at the very end of the TAF period or will be reflected in
the 00z issuance. For now, have kept MVFR CIGS through end of TAF
at TRI.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             36  57  35  64 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  37  53  32  61 /   0   0   0   0
Oak Ridge, TN                       37  54  32  60 /   0   0   0   0
Tri Cities Airport, TN              36  47  30  57 /  30   0   0   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...Winter Weather Advisory until 7 AM EST Saturday for Blount Smoky
     Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
     Mountains-Southeast Carter-Southeast Greene-Unicoi.

VA...Winter Weather Advisory until 7 AM EST Saturday for Russell-
     Washington VA-Wise.

&&

$$

SHORT TERM...DGS
LONG TERM....TD
AVIATION...KS