893
FXUS64 KMRX 181912
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
312 PM EDT Wed Sep 18 2024

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

.SHORT TERM...
(This evening through Thursday)
Issued at 311 PM EDT Wed Sep 18 2024

Key Messages:

1. A few showers and maybe a thunderstorm or two are possible
through this evening and again tomorrow afternoon.

2. Fog is likely again tonight, followed by clearing and warmer
temperatures on Thursday.

This Evening/Tonight

Currently this afternoon, tropical remnants from the Carolinas have
continued to weaken and are centered over northeast Tennessee to
southwest Virginia. A closed upper-low remains centered just to our
east. This has continued fairly weak northerly to northeasterly flow
and widespread cloud cover. Additional light showers remain
possible, along with an isolated thunderstorm as current data
indicates at least 250 J/kg of instability. This will be focused
further east closer to the better height falls. Otherwise, activity
will decrease overnight as diurnal heating is lost. With clearing
also expected, fog development is likely, especially in places that
see the better clearing and any rainfall.

Thursday

During the day on Thursday, the tropical remnants, including the
upper low, will shift further east. This will change the flow to be
more northwesterly throughout the column. In addition to some
orographic considerations, this system will continue to provide
broad but weak lift across the area. However, drier air will also be
filtering in from the northwest. Based on these considerations, rain
chances will be contained further north and east closer to the
better moisture, in addition to along the terrain. Overall, the
thermodynamics will be limited similar to today, but there is still
enough support for maintaining slight chance of thunder. The drier
air and eastward shift of this system will also allow for less cloud
cover and notably warmer temperatures than today.

&&

.LONG TERM...
(Thursday night through next Wednesday)
Issued at 311 PM EDT Wed Sep 18 2024

Key Messages:

1. Ridging will make conditions very warm and dry Friday to Monday.

2. Early next week, temperatures moderate closer to normal with some
low-end rain chances returning Tuesday.

3. Tropics might become a player during the latter half of next week.

Discussion:

Ridge of high pressure at 500 MB will be squeezed between an east
coast trough and a Rockies trough for days two-five Fri-Mon. This
means predominantly dry and very warm days during and surrounding
the weekend. This won`t be much help to the drought conditions.

The pattern will very slowly progress however, such that the ridge
will flatten along the northeast Gulf coast Mon and Tues, allowing
troughing to graze our area with some chance of precip Tues and Wed.

Late period questions will include whether troughing sharpens enough
to give us a drying NWly flow during midweek, which would also usher
in cooler air again. One of the complications is a potential
tropical system in the Gulf during Wed/Thur, and how it and the
trough interact with each other`s timing. The future track of said
tropical system may or may not be an influence on area precip come
late week -- i.e., does it dodge us through Tampa or moisten
us through Mobile?

&&

.AVIATION...
(18Z TAFS)
Issued at 122 PM EDT Wed Sep 18 2024

Some mid to even lower clouds will continue for the rest of the
day with some showers possible around TYS and TRI. If a shower
moves directly over the terminal (more likely at TRI), then
reductions to MVFR can be expected. Otherwise, most SCT/BKN decks
will likely stay just above 3,000 feet through the day. Overnight,
a decrease in cloud cover is expected with the main question being
how much fog develops. At this time, TRI is most likely to see
reductions to IFR or even lower, especially if some rain falls.
Some development is also anticipated at TYS, but the category was
kept higher because of less confidence. During the day tomorrow,
some lower clouds could linger later in the morning, but the most
places should stay VFR with light winds, generally from the north.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             66  89  65  92 /  10  10   0   0
Knoxville McGhee Tyson Airport, TN  64  86  63  89 /  10  10   0   0
Oak Ridge, TN                       63  86  62  89 /   0  10   0   0
Tri Cities Airport, TN              61  81  60  83 /  10  20   0  10

&&

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

$$

SHORT TERM...BW
LONG TERM....GC
AVIATION...BW