617
FXUS64 KMRX 051100
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
700 AM EDT Fri Jul 5 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 303 AM EDT Fri Jul 5 2024

Key Messages:

1. Scattered to numerous showers and thunderstorms expected today
ahead of a cold front. Marginally severe storms are possible,
mainly in the afternoon.

2. Another hot, humid day is expected today but with increasing
cloud cover and rain chances, we are not expected to reach Heat
Advisory criteria.

3. Some fog development is possible tonight in locations that
received rainfall.

Discussion:

A trough is moving into the Midwest. Weak troughing will be over
the Tennessee Valley today and tonight. At the surface, a cold
front will move through the region late tonight or early Saturday
with a shift to northerly winds. POPs start to increase late this
morning but the best chance for showers and thunderstorms will be
this afternoon and evening. NBM guidance seems to be running high
on POPs compared to the HREF but this latest run is a little
closer. HRRR guidance has more activity north of I-40 and along
the mountains. With good instability (CAPE over 2000 J/kg) and
plenty of low level moisture in place, there will be a marginal
risk for severe storms mainly in the afternoon during max heating.

With increasing clouds and rain chances, Heat Advisory criteria
will likely not be reached today. Although, it will be hot and
humid with heat indices around 100 for much of the Southern
Valley with highs in the lower 90s and dew points in the mid 70s.

Some showers and storms may linger into the evening hours but
mostly dry weather is expected after midnight. Fog development is
possible but will likely be limited to places that receive rain.

&&

.LONG TERM...
(Saturday through Thursday)
Issued at 303 AM EDT Fri Jul 5 2024

Key Messages:

1. Not quite as hot, but still slightly above normal through much of
the long term.

2. Mostly dry conditions expected across of the area this weekend in
the wake of a front Friday night into Saturday morning.

3. Diurnal showers and thunderstorms increase early next week
especially across the higher elevations.

Discussion:

In general throughout the entire extended, trend PoPs lower each day
compared to NBM guidance and deterministic models due to the drought
conditions developing over much of the area. Also, overall chances
of convection have been too high by ensembles and deterministic
models.

For Saturday, frontal boundary moves east of the Appalachians with
drier air advecting into the region. Any chance of convection will
be confided mainly over the far east Tennessee mountains and
southwest North Carolina. NBM probabilities remain highest there for
measurable rainfall.

For Sunday, ridge of higher theta-e remain across the southern
Appalachian mountains, especially over the Carolina`s. A low chance
of convection is expected over the far east Tennessee Mountains and
southwest North Caroline but overall dry conditions.

For Monday, boundary layer flow becomes more southeast/southerly
allowing for moisture return with theta-e ridge axis pulling into
east Tennessee. Better chance of diurnal convection especially for
the Mountains and Plateau as forcing orographic.

For Tuesday, Wednesday and Thursday, diurnal orographically forced
convection will continue. Continue to believe that the NBM PoPs are
too high due to the aforementioned above. There is a potential by
Thursday that some of the moisture from BERYL may move into the
Tennessee valley.

&&

.AVIATION...
(12Z TAFS)
Issued at 642 AM EDT Fri Jul 5 2024

VFR conditions are expected outside of thunderstorms today.
Scattered showers and thunderstorms are likely this afternoon but
some activity may linger into the evening. Some fog/low CIGs will
be possible late tonight but that is contingent on rainfall.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             93  74  92  72 /  80  50  20  10
Knoxville McGhee Tyson Airport, TN  92  74  90  69 /  80  60  20  10
Oak Ridge, TN                       90  72  90  68 /  80  50  10   0
Tri Cities Airport, TN              91  71  87  67 /  80  70  30  10

&&

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

$$

SHORT TERM...McD
LONG TERM....DH
AVIATION...McD