547
FXUS64 KMRX 031430
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1030 AM EDT Wed Sep 3 2025

...New UPDATE...

.UPDATE...
Issued at 1001 AM EDT Wed Sep 3 2025

Ageostrophic jet circulation and associated upper level
divergence over the southern Appalachians is working with weak
moisture convergence in the low/mid levels to promote continued
showers with occasional embedded rumbles of thunder this morning.
Made some minor adjustments to hourly PoP/sky cover grids to
better match latest trends. Have also added a short blip of
isolated nuisance water issues into the HWO as a few flood
advisories have been issued for portions of NE TN where locally
efficient and training rain has led to ~1.5" of rain in an hour.
Radar trends do suggest those rain rates have been starting to
trend downwards the last hour so nothing too standout in terms of
hazards, but would not be surprised if a few low lying or poor
drainage areas are observing minor ponding of water. This area of
showers is expected to gradually weaken and dissipate as we cross
into the PM hours, but some additional, more isolated, precip may
develop in diurnal fashion per latest CAM trends.

&&

.DISCUSSION...
Issued at 121 AM EDT Wed Sep 3 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.

2. There will be another chance for showers and storms Friday night
and Saturday, although chances remain mostly below 50 percent.

3. A cooldown is likely by Sunday after a cold front passage
late Saturday.

Discussion:

Shower activity may pick up late tonight. CAMs are split, some have
scattered coverage and some have nothing. Higher confidence in
showers and storms after daybreak today through the afternoon and
early evening as a deep trough sits over the Eastern U.S. A vort max
will move into the northern half of the region this afternoon aiding
in development. Several CAM members have scattered showers this
afternoon across the region. The HRRR has showers isolated and
mainly confined to SW Virginia and NE Tennessee closer to the better
lift. Instability will be pretty weak today with ML CAPE maxing out
around 700 J/KG.

By Thursday, a deep trough is still over the Eastern U.S. At the
surface, a weak cold front will stretch from Canada and into the
Tennessee and Ohio River Valleys. This does not look like a clean
frontal passage. This front will likely stall just north of our
region. Thursday afternoon will have a tad better instability with
ML CAPE around 600 to 1000 J/KG. There is a low end threat for a few
storms producing gusty winds during max heating Thursday.

Friday looks dry with increasing POPs Friday night and Saturday as a
cold front approaches. Generally POPs will remain below 50 percent.
This will be a clean frontal passage Saturday night or Sunday
morning bringing cooler temps and lower dew points. Also, a
noticeable wind shift to northerly winds.

&&

.AVIATION...
(12Z TAFS)
Issued at 700 AM EDT Wed Sep 3 2025

Scattered rain showers will continue through the morning hours
with isolated thunder possible at times. A lull is possible midday
before another round, maybe more confined to near TRI, this
afternoon/evening. Shower/storm activity will die down after
sunset. Fog development tonight will be dependent on cloud cover,
so confidence is low at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             83  64  86  66 /  20  20  40  10
Knoxville McGhee Tyson Airport, TN  81  62  83  65 /  60  20  50  10
Oak Ridge, TN                       80  61  81  63 /  50  20  60  10
Tri Cities Airport, TN              75  57  79  61 /  80  10  60  20

&&

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

$$

DISCUSSION...
AVIATION...