532
FXUS64 KMRX 221426
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
1026 AM EDT Sun Sep 22 2024

...New UPDATE...

.UPDATE...
Issued at 1023 AM EDT Sun Sep 22 2024

Forecast on track but with a few minor adjustments. Removed POPs
over the next few hours. Still expecting isolated showers and
storms to develop but not until around 12 to 1 PM. Also adjusted
hourly dewpoints and temps to match up with latest obs. Will send
new zones to get rid of morning wording.

&&

.SHORT TERM...
(Today and tonight)
Issued at 314 AM EDT Sun Sep 22 2024

Key Messages:

1. Unseasonably hot conditions again today. Temperatures around 10
degrees above normal.

2. A few spots may see a shower or possibly even a thunderstorm, but
most locations will remain dry.

Discussion:

We will remain under the influence of the upper ridge over the
region, providing another unseasonably hot day with temperatures
around 10 degrees above seasonal normals. Highs are expected to be
not far off of records for this date.

Some weak short wave energy will be rounding the edge of the ridge,
and a few locations may see a shower today or tonight. MLCAPES look
limited but enough modest instability should be available to include
the mention of thunder for this afternoon/early evening mainly
across the Plateau and southern/central valley areas. The best
chance for a shower looks to be north later tonight, and with the
loss of daytime heating will not include thunder.

Record Highs for Today:
Date    Chattanooga    Knoxville      Tri-Cities     Oak Ridge
09-22    96(1955)       96(1955)       90(2007)       95(1955)

&&

.LONG TERM...
(Monday through Saturday)
Issued at 314 AM EDT Sun Sep 22 2024

Key Messages:

1. Hot temperatures to persist Monday and lesser so on Tuesday as
clouds and increasing chances of rain begin to moderate temperature.

2. A strong thunderstorm is possible with strong gusty winds the
main threat Monday afternoon.

3. Unsettled weather to continue through Wednesday, bringing
beneficial rainfall.

4. Significant uncertainty remains after Wednesday.

Discussion:

We start the long term period on Monday with another hot, sultry day
courtesy of the longwave ridging reaching just far enough north to
affect us. Afternoon high temperatures will once again be several
degrees above normal. An extension of the jet stream will be
providing speed shear supportive enough of a strong thunderstorm or
two. HREF has 70 percent chance of SBCAPE exceeding 1000J, and SPC
has the northern half of our area under a marginal risk for a severe
wind gust or large hail. Lapse rates aloft don`t appear to be
supportive of a hail risk, so would think a strong wind gust is the
primary risk should a storm get strong enough.

After Monday`s storms, we remain in an unsettled pattern as a strong
longwave trough begins its foray into the heart of the country, and
smaller shortwaves keep rain chances up. Tuesday night into
Wednesday is increasingly looking wetter, with the latest Euro run
moving closer in line to EC-AI and GFS runs. This would be
supportive of more widespread showers across the valley, hopefully
bringing more legitimately beneficial rainfall.

Unfortunately, beyond Wednesday the forecast remains murky. We`re
now in range forecast wise to begin considering how the gyre
tropical disturbance currently in the Caribbean will evolve for our
local weather forecast. However, we still have significant
deviations from model to model and run to run on how our baroclinic
trough will evolve and move as it captures the tropical disturbance
moving northward out of the Gulf. Because of the track uncertainty
involved in the two core players, the QPF forecast is similarly a
disaster, and so lowered the deterministic amounts for now since
there`s no confidence on the higher potential. That`s not to say the
higher rainfall amount won`t happen, but the whiskers of uncertainty

&&

.AVIATION...
(12Z TAFS)
Issued at 528 AM EDT Sun Sep 22 2024

There may be a shower or even a thunderstorm around later today
mainly CHA/TYS and possibly a shower late in the period mainly
TRI, but probability is low so will not include. If any site does
see precipitation that would increase the chance for fog, but
right now probability for fog does not look high enough to include
in the TAFs. Will go with a VFR forecast for the period all
sites. Winds will generally be light.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             94  69  93  70 /  20  10  30  10
Knoxville McGhee Tyson Airport, TN  92  68  90  68 /  20  10  50  30
Oak Ridge, TN                       91  68  89  67 /  20  20  60  30
Tri Cities Airport, TN              87  63  84  64 /  10  20  60  30

&&

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

$$

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