441
FXUS64 KMRX 241737
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
137 PM EDT Tue Sep 24 2024

...New AVIATION...

.UPDATE...
Issued at 1058 AM EDT Tue Sep 24 2024

Forecast on track this morning with no significant changes. We
will continue to monitor the threat for any isolated strong to
severe storms through the day as convection further develops.

&&

.SHORT TERM...
(Today and tonight)
Issued at 340 AM EDT Tue Sep 24 2024

Key Messages:

1. Scattered showers and thunderstorms today. Best coverage this
afternoon into evening, in which time a strong thunderstorm is
possible with strong wind gusts.

Discussion:

A strong upper trough is diving down across the heart of the
country, strengthening the upper level flow across the Tennessee
Kentucky region. HREF Ensemble guidance has much of the area being
dry this morning, and outside of some morning fog the skies should
allow for some sunshine to reach the ground. Today is forecast to be
the last day of unseasonable heat, and with dewpoints near 70F, it
will be a muggy one. The combination of strong upper flow, and
humid, hot air will allow for another day of scattered showers and
thunderstorms to develop by the afternoon hours. Storms should
progress from west to east with time into the evening hours.
Effective shear today is around 45 knots, providing some potential
for strong to severe storms. Midlevel lapse rates still aren`t
overly impressive, and so severe hail seems very unlikely,
especially with freezing heights 12-14k feet above the ground.
Think the best is for a strong storm to be able to take full
advantage between peak heating and sunset and produce a wind gust
near or at severe criteria, otherwise most storms will be garden
variety thunderstorms.

The eastward progression of the upper low will come to a halt
Tuesday night into Wednesday, and with that halt, the approaching
cold front will stall out. Meanwhile continued upper flow and warm
moist air being advected northwards will continue to allow for
showers to form through Tuesday night, bringing additional rain
(and perhaps some thunder) to much of the area.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 340 AM EDT Tue Sep 24 2024

Key Messages:

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

2. Tropical remnants expected to impact the region during the second
half of the week. Exact impacts remain unclear but there continues
to be the potential for flooding and gusty winds.

Discussion:

An upper low will be parked to our west over the mid Mississippi
Valley region at the start of the period, and it is forecast to
meander but stay in the same general area for much of the period.
Out ahead of this upper low, moisture will continue to feed into the
area with the deep south and southwest flow. NAEFS data suggest PW
and moisture transport will be in the 90th percentile or higher
range at times for this time of year over parts of the area
Wednesday into Wednesday night. A weak nearly stationary frontal
boundary will be near our western border, and this combined with
divergent flow aloft will bring showers and storms. Very heavy
rainfall is possible which may lead to localized flooding,
especially in areas that see training convection.

The Thursday through Friday night time frame is dominated by the
question of the potential tropical system.  Right now, the NHC track
brings it ashore as as hurricane along the Florida Panhandle late
Thursday and then tracks the weakening system into our area sometime
around the early Friday time frame.  The details remain uncertain
this far out, and exact track and timing changes will need to be
monitored. However, this system has the potential to bring very
heavy rainfall and flooding, as well as the potential for strong
gusty winds with the strongest of these winds likely over the higher
terrain.

Models generally showing the remains of the tropical system getting
absorbed into the upper low to our west. We will remain in a
somewhat unsettled pattern with chances for showers and
thunderstorms each day.  Right now Saturday looks to be the day with
the lowest chances for precipitation as we dry out briefly behind
the tropical system. Temperatures will generally be not far from
seasonal normals each day during the extended period.

&&

.AVIATION...
(18Z TAFS)
Issued at 125 PM EDT Tue Sep 24 2024

An unsettled TAF period with isolated to scattered showers and
storms over the next 24 hours. A mix of VFR and MVFR conditions are
mostly expected.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             69  79  67  75 /  80  90  80  80
Knoxville McGhee Tyson Airport, TN  68  79  66  78 /  80  90  80  70
Oak Ridge, TN                       66  77  64  76 /  80  90  80  70
Tri Cities Airport, TN              65  78  65  77 /  60  80  70  60

&&

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

$$

SHORT TERM...
AVIATION...