743
FXUS64 KMRX 141919
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
319 PM EDT Wed Aug 14 2024

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

.SHORT TERM...
(This evening through Thursday)
Issued at 155 PM EDT Wed Aug 14 2024

Key Message:

1. Patchy fog possible in spots tonight. Thursday will almost repeat
today, with mostly sunny skies and an outside chance of a shower
or storm over the higher terrain. Except temperatures and humidity
a bit higher.

Discussion:

In the upper levels through tomorrow, troughing will continue to
shift east with ridging following close behind. NWly flow will
switch out of the south meaning, more humid air and warmer
temperatures will be headed our way.

Overall, Thursday will be a lot like this afternoon except
temperatures a couple of degrees warmer with increased humidity.
Isolated showers and storms, if they occur, will again be confined
to only the higher terrain Thursday afternoon and evening.

Overnight lows will be on the incline as well as the sticky
conditions. Like this morning, low stratus/fog will be possible
in spots again before sunrise.

&&

.LONG TERM...
(Thursday night through next Wednesday)
Issued at 155 PM EDT Wed Aug 14 2024

Key Messages:

1. Scattered to numerous showers and storms Friday into Saturday,
with some strong to severe storms possible Friday into Friday night.

2. Showers linger, at least in the mountains, Sunday into
Monday.

3. Drier for the remainder of the period.

Discussion:

Shortwave ridging continues over our region Thursday night into
Friday morning, but will be gradually shifting east in advance of a
synoptic scale trough/upper low moving into the Great Lakes region.
Shortwave energy will precede this trough, moving over our forecast
area during the day Friday. A few showers and thunderstorms may make
it into our northwest counties by midday Friday, then scattered to
numerous showers and storms can be expected Friday afternoon into
Friday night as additional energy moves through aloft. Models are in
decent agreement overall in showing effective bulk shear values in
the 20 to 30 kt range on Friday and Friday night. Agreement on
instability is not quite as high, but even the more conservative
guidance shows surface or mixed layer CAPE values in the 1000 to
1500 J/kg range. Still, this combo of shear and instability would be
supportive of some strong to severe storms. Damaging winds and very
heavy rainfall with the possibility of localized flooding currently
look like the main threats for Friday into Friday night. The SPC has
us in a marginal outlook area and this seems reasonable to me.

The cold front associated with the aforementioned trough/upper low
is forecast to move through Saturday with additional showers/storms
expected. Late Saturday through the remainder of the weekend the
Great Lakes low transitions into a deep trough across the eastern
CONUS as upper ridging builds over the southwest. Current trends in
model guidance indicate that Saturday night through Monday likely
will remain active, with at least some chances for showers in the
mountains in persistent northwest upslope flow. Temperatures should
remain around or perhaps slightly below normal, but more importantly
we`ll continue to have an influx of drier air from the northwest to
keep things comfortable.

&&

.AVIATION...
(18Z TAFS)
Issued at 133 PM EDT Wed Aug 14 2024

VFR to prevail with light and variable winds. Calm overnight. Low
chance of some patchy fog around TRI in the morning, so have
added a low end VFR VSBY TEMPO for a couple of hours. Not entirely
confident if this will occur, but obs this morning did have some
<10SM reported.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             71  91  72  91 /   0  10  10  40
Knoxville McGhee Tyson Airport, TN  67  90  70  89 /   0  10  10  50
Oak Ridge, TN                       66  89  70  88 /   0   0  10  50
Tri Cities Airport, TN              63  86  66  85 /   0  10  10  50

&&

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

$$

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