-- Discussion containing changed information from previous version are highlighted. --
962
FXUS64 KMRX 181052
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
652 AM EDT Tue Jun 18 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 348 AM EDT Tue Jun 18 2024

Key Messages:

1. Most of the area will remain dry today with isolated storms
possible, mainly in northwestern portions of our area.

2. Hot temperatures will continue with highs near 90 and tonight`s
lows in the mid 60s to low 70s.

Today

Currently early this morning, strong upper ridging is building in
with a 500mb high of 5,940m centered just to our east. At the
surface, high pressure extends from the Atlantic into the eastern
CONUS. With this initial setup, very mild conditions will continue
with drier air advecting from the southeast evidenced by PWATs
near to below 1 inch. Weak southeasterly flow over the mountains
will also help to provide at least some downsloping and add to
this drier trend. As such, most of the area can expect a dry and
similarly hot day with lessened humidity. Places further to the
northwest along the Plateau and southwest Virginia could see
isolated convection due to heating and better overall moisture.
However, instability will be pretty marginal (MLCAPE of 500 to 750
J/kg) and in the presence of very weak flow/shear at all levels.

Tonight

Overnight, the high pressure will continue to intensify and expand
from our east with 500mb heights reaching up to 5,960m in our area.
As the drier air continues to advect into the area, any convection
from earlier should diminish very quickly in the evening, providing
a dry and mild night. Places that do see rain could see fog, but
coverage will likely be fairly limited and focused more in river
valleys.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 348 AM EDT Tue Jun 18 2024

Key Messages:

1. Generally above average temperatures continue with hot weather
this weekend.

2. Diurnal convection possible this weekend with higher
probabilities for convection early next week as a frontal boundary
approaches the area.

Discussion:

Ridging continues across the Eastern CONUS through the weekend with
594 to 597 dam 500mb heights across the Appalachians. With the 850mb
ridge centered across the Ohio Valley and Central Appalachians,
subsidence and easterly/northeasterly flow will continue across our
area with downslope conditions and generally "drier" dewpoints in
the mid 60s. The combination of high LFC heights and mid-level
ridging will greatly limit instability with convection unlikely
through Friday.

By the weekend, a shortwave trough across the upper Mississippi
Valley is expected to flatten the Ohio Valley upper ridge on Sunday
into early next week. At this time, a weak surface cold front will
also approach our area. The 850mb ridge axis will shift eastward
with increasing southerly boundary layer flow. The increase in low-
level moisture and decreasing upper-level heights will boost
available instability, lower LFC heights, and increase probabilities
of diurnal showers and thunderstorms on Sunday and Monday across the
region. While deterministic guidance is uncertain with exact
precipitation coverage on Sunday into Monday, GEFS ensemble members
show likely probabilities of over 60 percent, especially across the
higher elevations, northeast Tennessee, and southwest Virginia.

&&

.AVIATION...
-- Changed Discussion --
(12Z TAFS)
Issued at 649 AM EDT Tue Jun 18 2024

VFR conditions will continue through the TAF period with some mid
to high clouds. A stray storm is possible but is very unlikely to
affect the terminals. Winds will also be from the southeast with
some gusts to near 20 kts possible at CHA. Tonight, winds will die
down with VFR expected to continue.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             91  70  90  69 /   0   0   0   0
Knoxville McGhee Tyson Airport, TN  90  67  89  67 /  20   0   0   0
Oak Ridge, TN                       90  67  89  67 /  10   0   0   0
Tri Cities Airport, TN              89  64  89  63 /  10   0   0   0

&&

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

$$

SHORT TERM...BW
LONG TERM....JB
AVIATION...BW