348
FXUS64 KMRX 250225
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
925 PM EST Sun Nov 24 2024

...New UPDATE...

.UPDATE...
Issued at 923 PM EST Sun Nov 24 2024

Forecast is on track this evening with just a few high clouds and
dry weather across the region. Dew point depressions are already
near zero across many valley locations, so patchy fog for
sheltered valleys and locations near rivers/lakes is probable once
again.

&&

.SHORT TERM...
(This evening through Monday)
Issued at 300 PM EST Sun Nov 24 2024

Key Messages:

1. Tranquil weather persists, but a front will approach just after
the end of the short term.

Discussion:

Tranquil weather will persist through much of the short term
period. A surface low will lift from the midwest into the western
Great Lakes region tonight and Monday, driven by a trough ejecting
from the northern Rockies. This will drive a front our direction,
but it arrives Monday night into Tuesday during the beginning of
the long term period. It`s possible that increased moisture
advection and lift ahead of the front could produce some showers
over the northern plateau by 00z Tue, but it`s likely the rain
holds off until the long term period.

Otherwise, the main concern for the short term is whether we get
any fog development again tonight. Increasing clouds should limit
fog to some degree, but expect there will be at least some patchy
stuff in the north tonight. Not sure there`s enough support in any
guidance to expect there will be dense fog though. Increasing
southwest moist advection should make for cloudy conditions
after daybreak tomorrow as well.

&&

.LONG TERM...
(Monday night through next Sunday)
Issued at 300 PM EST Sun Nov 24 2024

Key Messages:

1. A frontal passage early Tuesday will bring near normal
temperatures Tuesday through Thursday.

2. A more significant 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 Friday and Saturday. Northwest flow snow showers
Friday may bring light accumulation to parts of the Southern
Appalachians and southwest Virginia.

Discussion:

We start the period with a cold front knocking on our door from the
west that is forecast to move through late Monday into Tuesday. A
couple tenths of an inch to around a half inch of rain area-wide is
forecast with this "appetizer" of the holiday week. Winds will
increase coinciding with the front, but the parameters don`t line up
for any sort of mountain wave event. Wind gusts in the 25 to 35 mph
neighborhood will be possible across the higher elevations.

Precipitation with the aforementioned system will taper off into the
day Tuesday, turning dry for the next 24 to 36 hours or so into
Wednesday. Temperatures will be around normal with general highs in
the 50s and even low 60s for the southern half of the forecast area
Wednesday.

The entree of the week or the highlight of the long term, will be a
much stronger system late Wednesday and persisting into Friday. A
more equatorward extending shortwave trough will send a low pressure
system that develops off of the Rockies into Texas to our region by
late Wednesday. There will be a whole lot more moisture with this
system as flow originates from the Gulf beginning around early
Wednesday. QPF amounts have been consistent the past couple forecast
packages of rainfall amounts of more than 1 inch everywhere. 2 and 3
inch totals could be possible between Wednesday night and Friday
night, especially over higher terrain. This should and will be
monitored for the potential of flooding for our area. Unfortunately,
those that travel to their destinations on Thanksgiving Day, may be
dealt with moderate to heavy rainfall as the low center passes just
to our north Thursday with numerous to widespread rain. The cold
front itself will pass overhead sending temperatures downward
sometime during the night hours on Thanksgiving.

Beyond Thanksgiving, the transition to northwest flow will set the
stage for orographically lifted moisture. With cold temperatures
settling in behind the front, can expect this precipitation to
mostly fall as snow. Light accumulation of a couple of inches is
possible over the typical northwest flow favored locations. Much
colder and below normal temperatures will dominate the key message
for the Black Friday weekend kick off to the Christmas shopping
season. Shoppers (as well as those outdoors), will be welcomed with
highs locked in the 30s to 40s and overnight lows Saturday morning
plummeting to the 20s.

&&

.AVIATION...
(00Z TAFS)
Issued at 605 PM EST Sun Nov 24 2024

VFR conditions prevail this evening 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 begin to increase late in the
forecast period 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             41  68  49  59 /   0   0  70   0
Knoxville McGhee Tyson Airport, TN  37  67  49  57 /   0   0  70  20
Oak Ridge, TN                       38  65  47  57 /   0  10  80   0
Tri Cities Airport, TN              33  63  47  56 /   0   0  80  20

&&

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

$$

SHORT TERM...CD
LONG TERM....KS
AVIATION...JB