689
FXUS64 KMRX 022320
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
720 PM EDT Tue Sep 2 2025

...New UPDATE, AVIATION...

.UPDATE...
Issued at 715 PM EDT Tue Sep 2 2025

A few thunderstorms are still slowly working their way across the
region this evening. Strongest storms are producing a good amount
of lightning, and with the freezing levels being fairly low, we
could see some small hail produced by these storms as well with
this much lightning activity. Expect these storms to remain
sub-severe for the most part with brief heavy downpours and
occasional wind gusts looking to be the most impactful weather in
them. Setting sun will help cause these storms to decrease in
intensity with precipitation chances lingering through overnight.
Places that get rainfall this evening will be at greater risk for
fog developing in the morning.

&&

.DISCUSSION...
Issued at 131 PM EDT Tue Sep 2 2025

Key Messages:

1. Increasing chance of showers and thunderstorms Wednesday and
Thursday. Main concerns will be locally heavy rainfall and a
marginal threat of severe storms on Thursday.

Discussion:

Through the rest of the afternoon and evening, shower activity is
expected to be mainly west of I-75, ahead of an approaching
shortwave trough and a surface trough. A few isolated showers may
linger past sunset, mainly in the northern half.

A broad mid/upper level trough will maintain its position over the
eastern Conus for the next few days. Shortwave disturbances in
the cyclonic flow will bring enhanced rain chances to our area,
first on Wednesday and again on Thursday. The vort max now located
over IL will drop SE and track across KY tonight and tomorrow
morning, and SW VA tomorrow afternoon. Lift ahead of this vort max
will be focused across our northern sections, and mainly between
12-18Z. Instability is quite weak, with MLCAPE maxing out at
600-700 J/kg in northern sections, so thunderstorms should be
isolated at best.

A second shortave trough packs a little more punch on Thursday,
enhanced by a jet entrance region and a better defined surface
cold front. Better deep layer shear and MLCAPE in the 1000-1500
J/kg range will provide a more favorable environment for
thunderstorms, especially in northern sections closer to the
upper level jet forcing. Some storms will strong wind gusts will
be possible Thursday afternoon and evening.

The Thursday cold front appears to hang up just north of our area,
lingering there through Friday until another shortwave trough
moves around the longwave trough on Saturday. Friday looks dry,
followed by a cold front/trough passage that brings rain chances
on Saturday. At this time, moisture and instability looks too
limited for much of a severe threat, but this will bear watching.
Sunday appears drier and slightly cooler in the post-frontal air
mass, but this may be short lived as the Atlantic ridge begins to
assert itself again across the Southeast on Monday.

&&

.AVIATION...
(00Z TAFS)
Issued at 715 PM EDT Tue Sep 2 2025

Currently a few thunderstorms in east Tennessee could briefly
move into the TYS vicinity, but better chances they remain just
north of the airport. Have kept PROB30 in the TAFs to account for
this. If the airport does get rain we`ll likely need to introduce
more intense fog into the forecast.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             63  84  63  86 /  20  20  20  40
Knoxville McGhee Tyson Airport, TN  62  81  62  83 /  50  40  10  50
Oak Ridge, TN                       61  81  61  82 /  50  40  10  60
Tri Cities Airport, TN              57  75  57  79 /  40  70   0  60

&&

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

$$

DISCUSSION...
AVIATION...