-- Discussion containing changed information from previous version are highlighted. --
596
FXUS64 KMRX 011742
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
142 PM EDT Tue Jul 1 2025

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

.SHORT TERM...
-- Changed Discussion --
(This evening through Wednesday)
Issued at 133 PM EDT Tue Jul 1 2025

Key Messages:

1. Showers and thunderstorms ahead of a cold front this afternoon
into this evening. Heavy rain rates with the potential for isolated
flash flooding, along with a low chance of strong to severe storms
producing damaging winds.

2. Drier air moving in Wednesday.

Discussion:

The shortwave trough axis is still to our west as is the weak
summertime cold front.  As these features shift east, the frontal
boundary will likely be around our Plateau counties before sunset
and will move off to our south and east after midnight. We will see
numerous showers and thunderstorms ahead of the front.  RAP forecast
PW values ahead of the front in the 2.0 to 2.2 inch range are common
across the area, which continues to be favorable for very heavy rain
rates of 3+ inches per hour. This can quickly lead to flash flooding
issues, especially for urban areas with large amounts of impervious
surfaces, and areas with steep terrain and/or already wet ground
from recent heavy rainfall will also be especially vulnerable. While
available convective energy is not impressive, MLCAPE values will
likely reach 1500 to 2000 J/kg across much of the area which will
allow for some stronger updrafts. However, model soundings generally
look nearly saturated with height which will limit thermodynamic
damaging wind potential and increase tropical rain rates. Because of
this, the overall severe weather risk is low, but some isolated
strong gusty winds are possible with the strongest storms.

Behind the front, drier air begins to arrive later tonight into
Wednesday. Some weaker convection may linger over our  eastern areas
late tonight into Wednesday closer to the departing front.  However,
most locations will be precipitation free on Wednesday.  High
temperatures will be near seasonal normals.
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&&

.LONG TERM...
-- Changed Discussion --
(Wednesday night through next Tuesday)
Issued at 133 PM EDT Tue Jul 1 2025

Key Messages:

1. Mostly dry weather Thursday into the holiday weekend.

2. High temperatures Thursday will be around normal, then
temperatures will trend hotter for Independence Day into the weekend.

3. Moisture begins to increase by Monday into Tuesday with a better
chance for showers and thunderstorms.

Discussion:

An upper ridge will build over the region Thursday into Friday. With
subsidence and drier air over the area, we will see dry weather both
days, and the mostly dry weather will continue into the weekend.
High temperatures Thursday will be near seasonal normals, but by
Friday into the weekend highs will be around 3 to 5 degrees above
normal.  Those outdoors this holiday weekend will need to practice
heat safety and remain hydrated on these hot, mostly sunny days.

Models are not in good agreement for the latter periods, but
although they disagree on how quickly it happens they generally show
the ridge weakening its grip on our area and moisture increasing by
the early part of next week. We will see an increased chance for
showers and thunderstorms both Monday and Tuesday.
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&&

.AVIATION...
(18Z TAFS)
Issued at 1250 PM EDT Tue Jul 1 2025

Lingering MVFR from earlier will continue to scatter out with the
focus shifting towards showers and storms, which are already
developing north of CHA and west of TYS. Widespread rain is
expected at all of the sites, starting in the next couple of hours
and continuing well into the evening. TEMPOs for MVFR were
maintained at all sites, but reductions below this level are
certainly possible. Activity will diminish overnight with
potential for fog development at TYS and TRI. Southwesterly winds
today will become northerly by early tomorrow morning, following
the passage of the frontal boundary.

&&

.PRELIMINARY POINT TEMPS/POPS...
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Chattanooga Airport, TN             70  90  68  91 /  40   0   0   0
Knoxville McGhee Tyson Airport, TN  70  88  66  90 /  70  10   0   0
Oak Ridge, TN                       68  88  65  90 /  50   0   0   0
Tri Cities Airport, TN              68  84  63  86 /  80  20   0   0
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&&

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

$$

SHORT TERM...
AVIATION...BW