-- Discussion containing changed information from previous version are highlighted. --
431
FXUS64 KMRX 261919
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
319 PM EDT Wed Jun 26 2024

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

.SHORT TERM...
-- Changed Discussion --
(This evening through Thursday)
Issued at 313 PM EDT Wed Jun 26 2024

Key Messages:

1. Isolated showers and thunderstorms expected through Thursday. A
few strong storms are possible this afternoon and evening, with
wind damage being the main threat.

2. Slightly cooler tomorrow, but still near normal temperatures.

Discussion:

A weak upper level trough and associated cold front will swing
down from the northwest and into our area this evening. Latest
HRRR runs show isolated to scattered showers and storms developing
between 4 PM and 5 PM across the Cumberland Plateau, east TN
mountains and southwest VA mountains. Some of the showers and
storms across the plateau will likely drift down into valley
locations this evening. With marginal instability and very weak
shear in place, a few strong storms are possible. With dry air in
place from the surface to the midlevels, the main threat will be
damaging winds.

As we go further into the evening/overnight hours, additional showers
and storms will move in from the west. This is as forcing becomes
more favorable with the arrival of the trough. However, chances
for strong storms become less favorable during this time as
instability will be lower compared to pre-sunset hours.

Most areas will see little to no precip. However, any location
that receives a thunderstorm could see a quick 0.25 inches to 0.5
inches.

We will likely see a lull in the precip early tomorrow morning.
Then, as we begin to destabilize with daytime heating, see an
uptick in shower and storm development Thursday afternoon. The
best chance of seeing any precip will generally be from I-40 and
southward, which is closer to where the better forcing will be.
-- End Changed Discussion --

&&

.LONG TERM...
-- Changed Discussion --
(Thursday night through next Wednesday)
Issued at 313 PM EDT Wed Jun 26 2024

Key Messages:

1. Diurnal showers and thunderstorms through the weekend with
highest chances of showers and thunderstorms on Sunday.

2. Drier next week with ridge building across the region. Signals
for hot weather returning.

Discussion:

Shortwave trough on Thursday will flatten the ridge across the
Tennessee Valley and Southern Appalachians for Friday and into the
weekend. A stronger shortwave trough will move eastward across the
Great Lakes over the weekend with a cold front moving southeastward
towards our region on Sunday. Ahead of this front, diurnal
convection will be possible on Friday and Saturday, mainly across
the higher elevations. By Sunday, more widespread showers and
thunderstorms are expected ahead of this cold front. Model guidance
indicates MLCAPE values on Sunday afternoon expected to be in the
1500 to 2000 J/Kg range with weak bulk shear of 15 to 20 kt. This
will favor the possibility of some stronger storms, including strong
wind gusts, but the overall severe weather risk isolated and low.
The primary risks this weekend (mainly Sunday) will be related to
damaging winds and the potential of flash flooding due to heavy
rainfall rates as PW values rise into the 2.0 to 2.2 inch range
ahead of the front.

Behind this front, somewhat cooler and drier air is expected early
next week. However, ridging builds back in mid-week with a warming
temperature trend on Tuesday and Wednesday resulting in above normal
temperatures once again.
-- End Changed Discussion --

&&

.AVIATION...
(18Z TAFS)
Issued at 116 PM EDT Wed Jun 26 2024

Mostly VFR conditions expected through the period. However,
chances of isolated to scattered showers and storms will become
more favorable during this TAF period. Any shower or storm that
moves over a terminal may produce MVFR conditions. If precip
occurs before sunrise then fog is likely but not enough
confidence to include fog at this time.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             73  89  73  93 /  40  50  10  30
Knoxville McGhee Tyson Airport, TN  71  89  71  93 /  50  50  10  30
Oak Ridge, TN                       70  88  70  92 /  60  50   0  30
Tri Cities Airport, TN              68  87  67  91 /  50  50   0  40
-- End Changed Discussion --

&&

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

$$

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