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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KMRX 171745
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
145 PM EDT Wed Apr 17 2024

...New AVIATION...

.UPDATE...
Issued at 1118 AM EDT Wed Apr 17 2024

Light rain is slowing moving off the Plateau currently entering
the valley. Showers have not been impressive today by any stretch
of the imagination, with storm tops struggling to get high enough
to generate even a flash of lightning. Most thunder has been in
Alabama today, and the best chances of hearing thunder or seeing
lightning will most likely be confined to the Chattanooga metro
during shower passage. Temperature forecast for the remainder of
the day is time dependent on shower arrival, with high resolution
guidance being pessimistic on any additional warming for
locations receiving rain or after the rain. This jives up well
with the thick cloud cover and rain right at peak heating.
Locations closest to the mountains have the best chances to warm
up a few degrees this afternoon. Otherwise forecast is on track
today.

&&

.SHORT TERM...
(Today and tonight)
Issued at 236 AM EDT Wed Apr 17 2024

Key Messages:

1. Line of thunderstorms will try and move through in the early
afternoon.

2. Some of the storms could be strong with gusty winds and small
hail as the primary hazards.

Discussion:

Currently there are some weak radar returns present across the
eastern Tennessee Valley, but with how dry the lower levels of the
atmosphere are most of this is likely falling as virga. Will keep in
low end PoP chances through the early morning hours to account for
some light drizzle making it to the surface.

As we move into the daytime hours we should see a lull in
precipitation ahead of an incoming line of showers and thunderstorms
sparking off of a boundary from the convection to our west. The
timing of this boundary and any storms that spark off from it will
coincide with some of the stronger heating in the afternoon. CAMs
are not in great agreement with coverage of thunderstorms this
afternoon, with the most widespread coverage likely across southeast
TN and into AL/GA. However any storms that are able to fire off on
the boundary will have a moderately unstable atmosphere to tap into.
SBCAPE values look to climb up to around 1000 J/kg. The mid levels
of the atmosphere are also expected to be fairly dry with the
west/northwesterly winds over the region leading to increased DCAPE
and the ability for some of the stronger storms to bring gusty or
possibly damaging straight-line winds. Forecast soundings also
indicate about 20-40 knots of 0-6km shear meaning that storms could
maintain strength and also allow for hail development.

The peak time for strong to possibly severe storms will be starting
around 18z on the Plateau, and any remaining storms on the boundary
will be east of the mountains by 00z.

In addition to the storms the pressure gradient will tighten up
today allowing for gusty winds during the peak heating hours.
Strongest winds are expected in the higher terrain of the southern
Appalachian Mountains.

These storms and the generally overcast skies for much of the day
will keep temperatures in check, and about 5-10 degrees cooler than
what we experienced yesterday.

&&

.LONG TERM...
(Thursday through Tuesday)
Issued at 236 AM EDT Wed Apr 17 2024

Key Messages:

1. Showers and thunderstorms return for Thursday night and Friday.
There is a low chance of strong storms with gusty winds and hail
possible Friday.

2. Turning much cooler this weekend. Lingering showers are expected
this weekend, mainly Sunday as a Gulf Low develops over the
Southeast.

Discussion:

Thursday will be dry with weak ridging over the Southeast. Temps
will be warm with highs in the 80s on Thursday but guidance is
trending away from approaching the record highs.

Records for April 18th: CHA  90/2002   TYS  90/1896   TRI  87/2002

The next system starts to move in Thursday night as a weak low moves
into the Tennessee/Ohio Valleys with a weak shortwave aloft. The
best chance for showers and storms with this system will be late
Thursday night through Friday. The boundary slows as it moves
through the region. Instability may be high enough to produce some
strong storms with dew points in the 60s. Although, CAPE will be
fairly low around 400 to 500 J/kg and effective shear looks a little
low around 30 knots but these parameters look more favorable in the
Southern Tennessee Valley. Therefore, a few storm storms with gusty
winds and hail cannot be ruled out, mainly Friday morning and early
afternoon.

Saturday is trending drier with a clean frontal passage likely
Friday night. By Sunday, a weak Gulf Low moves into the Southeast
bringing a warm front over Georgia and Alabama. Showers will be
possible across the region on Sunday due to that boundary to the
south. This system looks progressive enough to dry us out by Sunday
night or Monday. Temps will be much cooler Saturday, Sunday and
Monday behind the cold front. Highs will be mainly in the 60s.

&&

.AVIATION...
-- Changed Discussion --
(18Z TAFS)
Issued at 141 PM EDT Wed Apr 17 2024

Band of rain showers will move across East Tennessee over the
next 4 hours. Best chances of a brief flash of lightning are
confined south of KTYS where heavier convection is. Accompanying
the rain showers are periodic VIS restrictions. After rain moves
out, conditions area wide will calm, with a low level inversion
setting up overnight over the valley. Unknown if CHA will
experience it to the same degree, but better chances for MVFR CIGs
at TYS and TRI from 12z through the end of the TAF.
-- End Changed Discussion --

&&

.PRELIMINARY POINT TEMPS/POPS...
-- Changed Discussion --
Chattanooga Airport, TN             63  86  64  79 /  10  10  60  60
Knoxville McGhee Tyson Airport, TN  61  84  62  76 /   0   0  60  80
Oak Ridge, TN                       61  85  62  76 /   0   0  60  70
Tri Cities Airport, TN              58  81  57  75 /   0   0  40  80
-- End Changed Discussion --

&&

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

$$

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