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324
FXUS64 KMRX 021854
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
254 PM EDT Sun Jun 2 2024

...New SHORT TERM, LONG TERM...

.SHORT TERM...
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(This evening through Monday)
Issued at 252 PM EDT Sun Jun 2 2024

Key Messages:

1. Showers, and perhaps a few afternoon thunderstorms, decrease in
coverage overnight with some areas of fog.

2. Mostly dry Monday with ridging building across the Southern
Appalachians. A chance of a few spotty showers across the
mountains.

Discussion:

The shortwave trough axis will move east of the region tonight
with weak ridging building in from the west. This will result in
clearing sky conditions. With low-level moisture, light winds, and
a clear sky, fog and low cloud development is expected across
portions of the area late tonight and into Monday morning. The
highest chances of dense fog will be across the western locations
of the forecast area, generally west of Knoxville and I-81.

Ridge axis and northwest flow aloft on Monday will result in
mostly clear to partly cloudy sky conditions during the afternoon
with dry conditions expected area-wide. Low chances (20 to 30
percent) of precipitation will continue across the higher
elevations of the mountains during the afternoon. However, with
poor lapse rates and limited instability, no severe weather
impacts would be anticipated.
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&&

.LONG TERM...
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(Monday night through next Sunday)
Issued at 252 PM EDT Sun Jun 2 2024

Key Messages:

1. Isolated showers and storms are expected on Tuesday with more
scattered to numerous coverage Wednesday to Wednesday evening.

2. A few strong to marginally severe storms are possible Wednesday
to Wednesday evening with damaging winds as the primary threat.
Isolated flash flooding is also possible, especially if there
are multiple rounds.

3. Rain chances will continue into Thursday with drier and milder
conditions Friday through most of the weekend.

Monday Night through Thursday

At the start of the period, ridging will be moving over the area
with a shortwave/closed low just west of the Mississippi River
Valley. At the surface, increasing southerly flow will be underway
as well. On Tuesday, ridging will shift further to the east with the
aforementioned shortwave approaching from the west. This will also
be accompanied by moisture advection, especially in southwestern
portions of the area. These locations will be the focus for
convection as the environment will be much less favorable as
evidenced by PWATs barely to 1 inch and minimal instability. Further
southwest where instability is present, values will likely be
limited to less than 1,000 MLCAPE with 20 kts or less of deep-layer
shear. Based on these indications, the threat for any strong to
severe storms will be very limited.

By Wednesday, the shortwave to our north and west will move overhead
with stronger southerly flow in the lower levels advecting even
better moisture into the area. A frontal boundary will also be noted
far to our northwest. By this time, many locations will have PWAT
values anywhere from 1.5 to 1.8 inches, reaching above the 90th
percentile for this time of year. With the continued heating and
better low-level moisture, the environment will likely be a lot more
unstable than Tuesday with MLCAPE likely exceeding 1,500 J/kg.
Overall winds will be fairly light, but they will be more veered
from the surface up to 500mb. Models are currently suggesting a
combination of scattered convection and/or a possible MCS arriving
from the northwest from late afternoon through the evening. The
evolution and timing of storms is still unclear, but the environment
is certainly supportive of some being strong to possibly severe.
With fairly high freezing levels and DCAPEs to 1,000+ J/kg, damaging
winds is really the main threat. Also, heavy rainfall rates due to
abundant moisture could lead to isolated flooding. Based on these
trends, HWO wording will be introduced. On Thursday, a westerly to
northwesterly flow pattern will remain in place aloft with the
frontal boundary approaching from the northwest. By this time, the
environment will be a lot more worked over, but additional showers
and a few thunderstorms are likely to continue.

Friday through Sunday

Towards Friday, troughing to our north and east will dig further
south, promoting a more northwesterly flow pattern. The frontal
boundary will likely push to our south, meaning winds near the
surface will follow the same northwesterly direction. Low-end rain
chances will be maintained, but a much drier column will likely keep
most places dry with a drop in temperatures to slightly below
normal. This northwesterly flow pattern will continue into Saturday,
keeping rain chances more limited. By Sunday, the boundary may begin
to be pulled back northward, but moisture and shower/thunderstorm
coverage still looks fairly limited.
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&&

.AVIATION...
(18Z TAFS)
Issued at 125 PM EDT Sun Jun 2 2024

Rain showers will continue to move east this afternoon with
generally clearing conditions from west to east. There is a low
chance of a thunderstorm in the vicinity of terminals this
afternoon, but with the probability only around 10 percent, have
left this out of the TAF at this time. The highest risk of a
thunderstorm this afternoon, around 20 percent, will be at CHA.
With clearing sky conditions tonight, especially near CHA and TYS,
widespread fog and low cloud development is expected across the
valley with MVFR and IFR impacts by Monday morning. Conditions
will improve to VFR by 14 to 15z Monday morning. Winds remain
light.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             66  87  67  88 /  10  10   0  30
Knoxville McGhee Tyson Airport, TN  63  85  64  87 /  30  10   0  30
Oak Ridge, TN                       63  85  64  86 /  20  10   0  20
Tri Cities Airport, TN              61  81  61  86 /  20  20   0  30
-- End Changed Discussion --

&&

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

$$

SHORT TERM...JB
LONG TERM....BW
AVIATION...JB