587
FXUS64 KMRX 181726
AFDMRX

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

...New AVIATION...

.UPDATE...
Issued at 1105 AM EDT Wed Sep 18 2024

Overall, fairly minimal changes were needed with the morning
update. Cloud cover has lingered a lot and has led to a slight
decrease in temperatures across the region. Also, mention of non-
measurable rain (sprinkles) was expanded based on continued
moisture and some indications from high-res models. Otherwise, the
forecast was kept largely the same.

&&

.SHORT TERM...
(Today and tonight)
Issued at 255 AM EDT Wed Sep 18 2024

Key Messages:

1. Isolated to scattered showers and possibly some thunderstorms,
are possible this afternoon and evening for similar areas that saw
precipitation yesterday - northeast Tennessee, southwest Virginia
& North Carolina, and in the foothills of the Southern
Appalachians.

2. High temperatures bounce back into the 80s today for much of
non-elevated areas.

Discussion:

What`s left of the tropical cyclone, is currently centered over
the Carolina`s providing some cloud cover and fog under broken
skies. Through the next 24 hours, a weak low will develop off of
the Virginia coast and try to get it`s act together as it deepens
some before reaching New England by tomorrow. Wrap around from
that system and residual energy leftover under troughing aloft,
will bring showers and maybe some thunderstorms back to the same
areas this afternoon and evening; most likely less in the form of
amounts. Chances for thunder are pretty low (< 30 percent), so
not expecting any severe weather. It doesn`t appear rain will be
as widespread as it was early yesterday either.

Again, the southern valley and plateau will not see much in the
way of any accumulating precipitation which is not what a lot want
to hear. Temperatures are expected to be several degrees warmer
this afternoon with readings back in the 80s for many. For
comparison, our climate sites ranged in the mid 70s and upper 60s
for highs Tuesday. Like some areas are seeing this morning, low
clouds and fog development may be possible again Thursday morning.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 255 AM EDT Wed Sep 18 2024

Key Messages:

1. Other than showers and an isolated rumble of thunder in the east
on Thursday, dry and progressively warmer conditions are expected
Friday through the weekend.

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

Discussion:

Not much has changed for the long term forecast. An upper low to our
east early Thursday will lift northeast to become an east coast
trough by Friday morning. Meanwhile ridging to our west, anchored
over Texas, will strengthen and expand to the east through at least
the first half of the weekend.

Still can`t rule out some isolated to scattered showers in the
northeast on Thursday, and possibly even a rumble of thunder, but in
general expect dry and increasingly warmer conditions Thursday
through Saturday. With the strengthening ridge and H85 temps warming
to 18-19C Friday and Saturday, feel pretty confident in saying some
locations in the south will likely see highs top 90 degrees. This
won`t be calendar day record territory, but it will definitely be
warm. Did undercut NBM dewpoints by a decent amount. Models suggest
deep mixing through this period, with increasingly dry air in place
so I went with a blend of CONSAll and the NBM 10th percentile to
bring dewpoints down a bit. Expect we`ll see some areas of sub-forty
percent RH on Friday and Saturday as a result. Winds should be light
though, so no notable uptick in fire weather concerns exist.

On Sunday, similarly strong ridging will remain in place, keeping
the area very warm and dry. By early next week, the main question
will be how troughing to our northwest will evolve. Some solutions
suggest a strong system to develop and progress to our north with
others showing more zonal evolution. Seems like the trends have been
towards a less dynamic system and more zonal upper pattern, but
there`s still quite a bit of uncertainty. In any case, some
moderation in temperatures and a return of low-end rain chances can
be expected.

&&

.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             84  65  88  64 /  10   0   0   0
Knoxville McGhee Tyson Airport, TN  81  64  85  61 /  10  10  10   0
Oak Ridge, TN                       81  63  85  61 /  10  10  10   0
Tri Cities Airport, TN              79  61  80  59 /  30  20  30   0

&&

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

$$

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