526
FXUS64 KMRX 281717
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
117 PM EDT Sat Jun 28 2025

...New SHORT TERM, LONG TERM, AVIATION...

.SHORT TERM...
(This evening through Sunday)
Issued at 102 PM EDT Sat Jun 28 2025

Key Messages:

1. Scattered showers and storms mainly during the afternoon hours.
Low probability of severe thunderstorms with gusty wind, heavy rain
rates, and frequent lightning.

2. Heat and humidity remain especially this afternoon, but slightly
below Heat Advisory criteria.

Discussion:

A weakness in the upper ridge across the region will result in
slightly lower max temperatures (although still hot and humid summer
conditions) and we should generally stay below Heat Advisory
criteria. Still, heat index values around 100 are occurring is some
valley locations mainly in the southern/central valley . It will be
vital to continue to practice heat safety across the region,
especially if outdoors for prolonged periods of time. Tomorrow
should be a bit less hot than today.

The weakness in the ridge will also allow more numerous mainly
diurnally driven showers and thunderstorms than have been seen in
recent days, although not everyone is guaranteed to see rainfall.
MLCAPE values of 2000 to 3000+ J/kg and DCAPE between 800-1000 J/kg
this afternoon will continue to support a few strong to severe
thunderstorms with damaging downburst potential.  PW values around
1.4 to 1.8 inches will support some heavy rain rates and the
potential of some isolated flooding of low lying areas. Convective
coverage will begin to diminish this evening with the loss of
daytime heating.

For tomorrow models show less instability than today but PW values
will tick up more into the 1.5 to 1.9 inch range.  We will see
scattered to numerous showers and thunderstorms again especially
with peak heating, and while the strong to severe storm threat will
be lower given the more limited instability (HREF shows mean MUCAPES
generally less than 2000 J/kg), a few storms may still become strong
to marginally severe with damaging wind gusts the primary severe
threat. In addition, given the plentiful moisture there will
continue to be a threat of localized flooding.

&&

.LONG TERM...
(Sunday night through next Saturday)
Issued at 102 PM EDT Sat Jun 28 2025

Key Messages:

1. Higher rain chances into the early part of the week. Isolated
strong or severe storms and localized flash flooding are possible
each day, with the flooding risk highest Monday/Tuesday.

2. A cold front approaches the area Tuesday, with the possibility of
less precipitation coverage Wednesday through Friday if the front
moves southeast of the region.

Discussion:

The weakness in the ridge will continue to produce quite a bit of
mainly diurnally driven convection Sunday afternoon and evening. A
few strong to severe pulse thunderstorms will be possible again in
the afternoon with the primary risk being damaging winds. PW values
will generally range from 1.7 to 1.9 inches Sunday. This will
produce some moderate to heavy rainfall rates with a threat of
localized flooding.

Model and ensemble guidance indicates more tropical moisture ahead
of the frontal boundary early next week. This will bring PW values
into the 1.8 to 2.2 inch range across the forecast area by Monday
and Tuesday ahead of an upper-level trough and associated cold
front. This very moist airmass will promote very heavy rainfall
rates exceeding 3 inches per hour in heavier downpours. Any training
or slow moving convection will likely lead to flash flooding
concerns, especially for urban areas with poor runoff and other
flood prone areas. The isolated severe risk will continue as well,
mainly for some isolated downburst winds.

The cold front is expected to slowly move southeast across the
region Tuesday into Tuesday night with drier air arriving from the
northwest. Much of the model data continues to suggest the front
will make it to our southeast before stalling, but as is often the
case with these weak summertime fronts there is still significant
uncertainty about this.  Right now, we expect it to be drier across
our area Wednesday, although the front may not fully clear our
southern areas by Wednesday and the highest PoPs will be southern
and eastern areas. Drier conditions are expected for Thursday and
Friday, but given uncertainty about the extent of the drying in
these longer ranges there is still a low chance of convection with
peak heating especially south. High temperatures that had been
running near to slightly above normal for much of the long term
period will likely begin to edge up slightly by Friday.

&&

.AVIATION...
(18Z TAFS)
Issued at 102 PM EDT Sat Jun 28 2025


Another round of diurnal afternoon and evening showers and
thunderstorms is expected, but confidence on if they will make
over the terminals is not high so maintained the PROB30 thunder
groups. Tonight patchy fog and/or low clouds are likely, mainly
at TRI, and will go with MVFR conditions at TRI late tonight
although lower conditions will be possible especially if rain
occurs there later today. Winds will generally be light, but will
likely become gusty with any thunderstorms.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             71  92  72  89 /  20  60  20  70
Knoxville McGhee Tyson Airport, TN  70  90  72  90 /  30  50  20  70
Oak Ridge, TN                       70  90  70  89 /  20  60  20  70
Tri Cities Airport, TN              68  88  68  88 /  40  50  30  60

&&

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

$$

SHORT TERM...BW
LONG TERM....BW
AVIATION...