497
FXUS64 KMRX 131731
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
131 PM EDT Tue Aug 13 2024

...New AVIATION...

.UPDATE...
Issued at 909 AM EDT Tue Aug 13 2024

Forecast on track this morning with only minor tweaks to hourly
temps and dewpoints to match up with latest obs.

&&

.SHORT TERM...
(Today and tonight)
Issued at 256 AM EDT Tue Aug 13 2024

Key Messages:

1. Mix of clouds and sun, can`t rule out a shower in higher
elevations, but otherwise dry and warm again today.

Discussion:

Northwesterly flow aloft caused by troughing to our northeast
persists for another day today. Down closer to the surface, winds
will remain generally northerly, helping keep our mild mannered
airmass in place for a bit longer. There`s been some light returns
early this morning across Kentucky, however observations indicate
the rain is either not reaching the ground or its not measurable. It
is conceivable though that some locations across southwest Virginia
might see a sprinkle or two before activity dissipates around
sunrise today.

For this afternoon, HREF guidance really is not indicating much in
the way of convection, with the subsidence aloft helping to cap the
atmosphere. Expecting today to be another dry summer day, with a
slight chance of a shower in the East Tennessee mountains along the
North Carolina border. Tonight should then be another calm, quiet
night much like the last few nights. Guidance indicates some
potential for patchy fog early Wednesday morning, though left it out
of the forecast for now.

&&

.LONG TERM...
(Wednesday through Monday)
Issued at 256 AM EDT Tue Aug 13 2024

Key Messages:

1. Mostly dry weather for Wednesday into Thursday.

2. Chances for showers and storms will increase in the
Friday/Saturday time frame, then decrease again for the latter
periods.

Discussion:

We start the period with an upper ridge to our west and a trough
over the East Coast, along with surface high pressure extending into
our area from the north.  The upper ridge will edge east into our
area Wednesday into Thursday, but will be flattening out as an upper
trough digs into the western Great Lakes region and Mississippi
Valley. Models differ on how quickly the upper ridge over our area
will break down with short wave energy moving out ahead of the main
trough, but overall the Wednesday and Thursday time frame look to be
mostly precipitation free as moisture, especially in the lower
levels, will be slow to increase. Will carry slight chance PoPs in
some of the higher terrain Thursday, but the better chance for
precipitation will occur in the Friday/Saturday time frame as the
main upper trough moves into our area and a cold front moves
through. Models suggest an uptick in effective shear as the trough
moves in although right now mean GEFS SBCAPES are limited with
values generally around 1250 J/kg or less. We will continue to keep
an eye on the potential for a few stronger/severe storms Friday
and/or Saturday given the uptick in shear, especially if available
convective energy trends higher. Right now the highest chances for
showers and storms looks to be Friday, with most models suggesting
drier air starting to filter in on Saturday.  However, the timing of
how quickly the front moves through and the drying commences is
still uncertain.

The upper trough is forecast to persist over the eastern CONUS
Sunday and Monday. We will remain in northwest flow aloft and there
may be some weak short wave energy moving through the flow during
these latter periods, but available moisture/convective energy looks
limited so will have lower chances for convection both days.

&&

.AVIATION...
(18Z TAFS)
Issued at 121 PM EDT Tue Aug 13 2024

VFR conditions through the period at all sites with light
northerly winds at CHA and TYS with VRB at TRI. A few data sources
showing fog at TRI tonight but low confidence so will not include
in this TAF set.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             69  91  70  91 /   0   0   0  10
Knoxville McGhee Tyson Airport, TN  64  89  66  89 /   0   0   0  10
Oak Ridge, TN                       64  88  66  88 /   0   0   0  10
Tri Cities Airport, TN              61  85  61  86 /   0  10   0  10

&&

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

$$

SHORT TERM...
AVIATION...