736
FXUS64 KMRX 240548
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
148 AM EDT Tue Sep 24 2024

...New AVIATION...

.UPDATE...
Issued at 834 PM EDT Mon Sep 23 2024

Update this evening mainly tweaked PoPs for the rest of the
evening to better come in line with current radar trends. Expect
the coverage of storms to continue to come down as the evening
progresses, but they won`t completely go away overnight. Have also
tweaked the fog forecast with areas that saw moderate rainfall
this afternoon the most likely locations to see patchy fog
overnight. However with the sun setting the threat of strong
thunderstorms should be behind us and hopefully some additional
places that need rain can get a quick shower tonight.

&&

.SHORT TERM...
(This evening through Tuesday)
Issued at 239 PM EDT Mon Sep 23 2024

Key Messages:

1. Isolated to scattered showers and thunderstorms continue this
afternoon and evening. A few strong to severe storms are possible,
but not likely. Locally heavy rain and strong wind gusts are the
main threats.

2. Fog likely tonight for any area(s) that receive rainfall today.

3. Additional showers and storms tomorrow, a few storms may be
strong to severe. Locally heavy rain and strong wind gusts are the
main threats.

Discussion:

Isolated to scattered showers and storms are ongoing across the
area. The current environment is marginally conducive for strong to
severe storms. The limiting factors are little to no shear in the
lower levels, marginal MLCAPE, and poor mid level lapse rates. For
these reasons, strong to severe storms are not likely but a low-end
probability still exists, mainly due to 30kts of shear in the mid to
upper levels. The main threats with any stronger storm will be
strong and gusty winds and locally heavy rainfall.

Shower and storm coverage will decrease after sunset but additional
isolated activity is expected through the night. Any area(s) that
receive rainfall this afternoon and evening will likely see fog
overnight.

Tomorrow, POPs will further increase as shortwave energy and upper
level support increase ahead of an approaching cold front. Not
everyone will see rain, but these are the highest POPs we`ve had
in quite a while with chance and likely POPs in for most areas.
Tomorrow`s strong to severe storm chances will be slightly higher
than today, though we are technically still in a marginal risk
from SPC. The environment looks better with 0-3km shear around
20kts, and mid-level lapse rates closer to 6 deg C. I expect
storms to be better organized tomorrow, thus increasing our
chances of seeing an isolated strong to severe storm. The best
chances will be during the mid afternoon and into the early
evening hours.

&&

.LONG TERM...
(Tuesday night through next Monday)
Issued at 239 PM EDT Mon Sep 23 2024

Key Messages:

1. Unsettled weather will continue throughout the long term period
with temperatures returning to more seasonal in nature.

2. Increasing confidence in tropical remnants impacting the region
during the second half of the week. Exact impacts remain unclear but
there continues to be an increasing potential for flooding and gusty
winds.

Discussion:

By Tuesday night a frontal boundary will be approaching the region
ahead of an upper level trough digging into the southern Mississippi
River Valley. A few strong to severe storms cannot be briefly ruled
out late Tuesday evening given instability around 1000J/kg and
effective bulk shear of 30+ kts, though, strong to severe threat
should gradually diminish with waning instability overnight. On the
contrary, the chance for showers and storms will persist throughout
Wednesday as a closed low is expected to develop from the
aforementioned trough. This will largely driven by upper level
divergence as thermodynamic profiles become noticeably less
favorable with persistent cloud cover expected.

During this time frame, the current potential tropical cyclone 9 is
expected to develop into a Hurricane by Wednesday morning per latest
National Hurricane Center forecast. Model guidance has pretty good
agreement in the general northward direction of this Hurricane into
the second half of the week, which would bring remnants of the
system to our doorstep Thursday and Friday, persisting the chances
for unsettled weather. We are expecting the threats for gusty
winds(especially in downslope favored locations of the East
Tennessee mountain) and chances for flash flooding and/or river
flooding to be on the increase during this time frame.

NBM probabilities of 2.5" of QPF into Friday afternoon generally
range from the 30-60%. The flooding threat will be partially
contingent on rainfall received during the first half of the week
and how saturated soils may be leading up to the tropical remnants.
As for gusty winds, we will be keeping eye on the potential for east-
southeasterly H85 flow of 30-50kts to bring downslope enhanced winds
across the East Tennessee mountains and foothills at times. Again,
details should become more clear as this system further develops and
the range of possibilities in the track decrease. This tropical
system is expected to be absorbed by the closed low to our west by
the weekend. This will continue to linger the chances for
precipitation throughout the remainder of the extended period.

&&

.AVIATION...
(06Z TAFS)
Issued at 141 AM EDT Tue Sep 24 2024

Scattered showers with an embedded flash or two still moving
across to start the period, though a period of no rain is expected
until afternoon convection begins again. Scattered cloud deck
should give way to MVFR or IFR VIS early this morning, conditions
will improve back to VFR after sunrise. An additional round of
scattered strong TS is expected after 18z, though impacts
directly to terminals is unknown. Heavy rain and strong winds
possible during any storm with attendant VIS restrictions.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             91  69  81  68 /  40  80  90  60
Knoxville McGhee Tyson Airport, TN  89  68  82  67 /  60  90  80  60
Oak Ridge, TN                       87  66  79  65 /  70  90  90  60
Tri Cities Airport, TN              85  66  80  64 /  70  70  70  50

&&

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

$$

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