686
FXUS64 KMRX 271130
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
730 AM EDT Thu Jun 27 2024

...New AVIATION...

.SHORT TERM...
(Today and tonight)
Issued at 325 AM EDT Thu Jun 27 2024

Key Messages:

1. Area of showers this morning will become scattered for today.

2. Clouds will keep highs some 5 to 8 degrees lower than
yesterdays.

3. Patchy areas of fog expected tonight some may be locally dense.

Discussion:

Radar and satellite shows a short-wave moving across the Plateau
counties producing an area of showers over much of the area early
this morning. This wave will move east of the area with only a
weak shear axis over the region today. Large area of showers will
diminish quickly early this morning.

For today, weak shear axis and frontal boundary/inverted surface
trough will remain over the region. Instability will be marginal
with MLCAPES of 500 to 1000. DCAPES up to 800 across CHA and
mid-level lapses are low. Overall, strong storms are not expected
today.

Due to loss of daytime heating and frontal boundary moving south
of the area, convective activity will end by sunset with partly
cloudy sky. Patchy areas of fog is expected tonight with some
locally dense.

&&

.LONG TERM...
(Friday through Wednesday)
Issued at 325 AM EDT Thu Jun 27 2024

Key Messages:

1. Scattered to numerous showers and thunderstorms this weekend.

2. Drier next week with ridge building across the region.

3. 100+ degree heat indices this weekend and again Wednesday.

Discussion:

The pattern in recent times of a southern ridge and a northern storm
track will continue across the nation. Those progressive systems to
the north will continue to influence the southern high pressure
center, as it shifts east to west and back again. We will experience
drier and hotter weather when the ridge centers over the southeast,
and a stormier pattern when the ridge centers over the southwest
states. Thus, with the ridge over Texas this weekend, a surface
boundary will meander over our area beneath a WNWly flow aloft, thus
we expect rounds of showers and embedded tstms beginning Friday but
maxing out over the weekend. Then for the new work week, with the
southern ridge recentered over the lower Mississippi Valley, our
area will be generally protected from encroaching weather systems,
with only diurnal high-terrain convection Mon-Wed.

Under the influence of the frontal boundary this weekend, daytime
highs will come down a little, but dewpoints will rise with the
precip-moistened topsoils. So heat indices exceeding 100 degrees can
be expected, particularly in the southern TN Valley, during weekend
afternoons. Once the ridge reasserts itself next week, rain will be
scanty, and dewpoints and heat indices will drop. But max temps will
gradually return to the mid 90s, which means 100+ degree heat
indices resume Wednesday.

Overall the severe weather risk this weekend will be isolated. The
primary risks this weekend 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.

&&

.AVIATION...
(12Z TAFS)
Issued at 701 AM EDT Thu Jun 27 2024

An upper level shear axis along with an inverted surface trough
over the Tennessee valley will keep a chance of showers and
possibly a thunderstorms for CHA/TYS through this afternoon.
Otherwise, scattered to broken areas of low MVFR ceiling across
all of the TAF sites this morning.

For tonight, VFR conditions initially will give way to MVFR,
possibly IFR conditions due to fog development. Confidence is low
of the extent and severity of the fog.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             88  73  92  76 /  60  20  30  20
Knoxville McGhee Tyson Airport, TN  87  70  92  74 /  40  10  30  30
Oak Ridge, TN                       86  69  92  73 /  40  10  30  20
Tri Cities Airport, TN              84  66  90  71 /  50   0  30  20

&&

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

$$

SHORT TERM...DH
LONG TERM....GC
AVIATION...DH