612
FXUS64 KMRX 250850
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
350 AM EST Mon Nov 25 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
(Today and tonight)
Issued at 324 AM EST Mon Nov 25 2024

Key Messages:

1. Mild temperatures today with increasing clouds ahead of an
approaching cold front.

2. Showers spread into the area from the west this evening and
exit by sunrise Tuesday morning.

Discussion:

A low pressure system will be tracking NE from the Mid-MS Valley
to the Great Lakes today, pushing a cold front across TN tonight.
Ahead of the front today, we will have a S-SW low level flow that
will transport moisture and isentropic lift through the day. The
shallow depth of moisture and lift will mean only an increase in
cloud cover, as 700 mb and above remains quite dry. A SW flow up
the Valley may produce some gusty winds to 20-25 mph this
afternoon. The SW direction of winds at 850 mb does not suggest
mountain wave winds; gusts around 25-35 mph are more likely for
most of the higher elevations. This SW flow will produce mild
temperatures today in the 60s.

Forcing near the approaching cold front increases this evening,
and a line of showers is expected to cross the area from west to
east mainly between 03Z and 09Z. Some isolated thunderstorms may
be possible in the Plateau, with convection weakening as it moves
east through the night. Total QPF amounts in the range of a quater
to half inch are expected.

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 324 AM EST Mon Nov 25 2024

Key Messages:

1. A frontal passage that will come through early Tuesday morning
will lower high temperatures to near normal through Thursday.

2. A more significant weather system moves in late Wednesday and
through Thanksgiving into Friday. A general 1 to 2 inches of rain
with this system and over 2 inches possible across parts of the
higher terrain.

3. Much colder temperatures Friday through Sunday. Northwest flow
snow showers early Friday may bring light accumulation to parts of
the Southern Appalachians and southwest Virginia. Another weak
system brings another chance of snow showers Saturday night and
Sunday to NE part of forecast area.

Discussion:

A cold front passes through the area early Tuesday. Only light
rainfall amounts linger Tuesday morning near the northeast Tennessee
mountains. As high pressure builds in behind the front skies clear
with temperatures several degrees cooler than Monday but near
average for late November.

The main rainmaker type system and highlight of the long term part
of the forecast will be a much stronger system as it approaches late
Wednesday and persists into Friday. A more southern shortwave trough
will bring a low pressure system that develops over the southern
plains Wednesday afternoon and into the lower Mississippi Valley
Wednesday night. The Gulf of Mexico will be pumping alot of moisture
northward as southerly flow brings a stream north into the Tennessee
Valley. QPF amounts for this system are lower than yesterday with 1
to 1.5 inches for the 36 hours from 18Z Wednesday to 12Z Friday.
Isolated higher totals near 2 inches higher elevations in the east
Tennessee mountains. There still could be a potential of flooding
for parts of the eastern Tennessee Valley but most locations are
still suffering from drought the last couple months. a period of
moderate to heavy rainfall is possible as the low center passes just
to the north Thursday morning. Behind the front much colder airmass
moves in by Thursday night.

As the region transitions to a northwest flow pattern Thursday night
and Friday, orographically lifted moisture will drop snow levels in
the much colder airmass. The moisture is expected to dry out quickly
by Friday afternoon with only small amounts of snow in Southwest
Virginia and east Tennessee. Amounts look to be mainly less than 1
inch but up to about 2 inches in the highest elevations. The big
change in the forecast will be temperatures Friday through Sunday in
the lower to mid 40s days and 20s at night. A weak shortwave
traveling southeast in the northwest flow may bring another brief
period of snow to northeast Tennessee and southwest Virginia
Saturday night and into Sunday.

&&

.AVIATION...
(06Z TAFS)
Issued at 1241 AM EST Mon Nov 25 2024

VFR conditions prevail overnight at all sites. Some VCFG will be
possible near terminals, especially near TRI and TYS late tonight
and Monday morning; however, high clouds will likely limit overall
fog coverage. Clouds at the VFR/MVFR margins begin to increase
after sunrise ahead of a frontal boundary. Winds remain generally
light and shift to the SW Monday afternoon ahead of the front.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             69  48  59  38 /   0  80  10   0
Knoxville McGhee Tyson Airport, TN  68  49  57  36 /   0  80  10   0
Oak Ridge, TN                       65  46  57  35 /  10  80  10   0
Tri Cities Airport, TN              66  48  56  32 /   0  80  10   0

&&

.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&

$$

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