-- Discussion containing changed information from previous version are highlighted. --
463
FXUS64 KMRX 231315
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
915 AM EDT Mon Sep 23 2024

...New UPDATE...

.UPDATE...
-- Changed Discussion --
Issued at 914 AM EDT Mon Sep 23 2024

No forecast updates this morning as everything is currently on
track. Will send out new zones to get rid of morning wording.
-- End Changed Discussion --

&&

.SHORT TERM...
(Today and tonight)
Issued at 323 AM EDT Mon Sep 23 2024

Key Messages:

1. Isolated to scattered showers and thunderstorms around during the
period. A few storms this afternoon may be strong to severe with
damaging winds the main threat.

3. Hot again today, temps around 5 to 10 deg above normal.

Discussion:

We start the period with the upper ridge still over our area and an
upper trough to our west over the Plains. Heights will be decreasing
over our area as the ridge axis shifts east and the upper trough
slowly edges east. Short wave energy ejecting out ahead of the upper
trough will move across our area, bringing an increased chance for
showers and storms. Convective energy looks to be modest, with
MLCAPES possibly approaching 1000 J/kg, but while low level shear
looks quite weak the deeper layer shear will increase with 0-6km
shear approaching or exceeding 30kts. This increases the potential
for cell organization and the possibility of some damaging wind
gusts especially this afternoon/early evening, although the overall
threat of severe storms remains low.

It will be hot today again, with high temperatures around 5 to 10
degrees above normal expected. Given a long enough precip free period
and sufficient sunshine, the daily record may be threatened again
today at CHA.

Record Highs for Today:
Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge

&&

.LONG TERM...
(Tuesday through Sunday)
Issued at 323 AM EDT Mon Sep 23 2024

Key Messages:

1. Temperatures start hot Tuesday, then subside to more seasonal
conditions for the remainder of the week.

2. Strong to severe thunderstorms possible again Tuesday afternoon,
wind and hail primary risks.

3. Unsettled pattern to continue through Wednesday with additional
rain chances area wide.

4. Increasing confidence on tropical system remnants being pulled
into East Tennessee, though exact timing is still unknown.
Significant rainfall is increasing in likelihood.

Discussion:

Tuesday is the final hot summer like day of this recent late season
heat wave, with temperatures getting 5 to 10 degrees above normal
once more. Meanwhile a weak low in northern Illinois in advance of
our main show upper trough will be helping to advect warm, moist air
northeast. Aloft strong upper level winds (for September anyways)
will help provide effective shear of 40 to 45 knots. This combined
with the HREF`s high probabilities of 1000J of CAPE and CAMs
indicating a relatively untapped daily atmosphere by the time
afternoon heating is peaking indicate a potential for strong to
severe thunderstorms, supportive of both a wind and hail threat in
the strongest of thunderstorms. The Storm Prediction Center has
likewise brushed a broad spectrum of the area into a marginal risk
(or level 1) of severe storms.

Moving past Tuesday into Wednesday, flow becomes more parallel with
our terrain and guidance is indicating more showers and
thunderstorms on Wednesday. Up to this point the better convection
chances have been across northern Tennessee into Virginia, but now a
more broader regional area will be able to receive rainfall. Shear
will still be present into Wednesday, but severe potential will be
more dependent on CAPE given potentially ongoing rain showers by
then.

Beyond Wednesday we are watching the progress of the tropical system
in the western Caribbean. Ensemble mean trajectories have begun to
narrow on a solution, though timing is still uncertain. The biggest
risk with the tropical system will be rainfall, though exact track
may also bring a non-thunderstorm wind threat to East Tennessee.
Ensemble probabilities for rainfall greater than 4 inches through
the whole week have begun to appear, up to 20% for areas along the
Georgian border. Despite the severe drought conditions that are
ongoing, too much rain in too little of a time period can still
present a flood risk. Since the system hasn`t even officially been
designated yet, we still have plenty of time to watch for changes in
track, timing, and potential intensity and how those will influence
impacts in our part of the Mid South. Ensemble consensus does expect
the upper low to absorb the tropical low and then meander slowly
through the wider Ohio River valley through the upcoming weekend,
bringing additional rain chances.

&&

.AVIATION...
(12Z TAFS)
Issued at 543 AM EDT Mon Sep 23 2024

There will be some showers and thunderstorms around during the
period. Will carry showers at TRI early and will try to time the
most likely period for thunderstorms with a prob30 thunderstorm
group all sites. Fog development late is possible but given
uncertainties about where rain will occur and potential cloud
cover, the probability at any given site looks too low to include
for now. Outside of any showers/storms, will go with a VFR
forecast for the period all sites. Winds will generally be light,
although may become gusty with any storms.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             93  70  90  69 /  30  20  30  60
Knoxville McGhee Tyson Airport, TN  91  68  89  68 /  50  30  50  70
Oak Ridge, TN                       89  67  87  66 /  50  20  50  70
Tri Cities Airport, TN              84  65  84  65 /  60  30  70  70

&&

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

$$

SHORT TERM...
LONG TERM....Wellington
AVIATION...