Johnson City, Tennessee 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

655
FXUS64 KMRX 252359
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
759 PM EDT Sat Jul 25 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 737 PM EDT Sat Jul 25 2026

- Scattered showers and storms are expected tonight. If multiple
  storms track over one location, isolated flooding will be
  possible.

- A warming trend begins tomorrow into the new work week. Monday
  and Tuesday will be the hottest days as heat indices in the mid
  90s to low 100s become more commonplace, especially in the
  central and southern valley.

- Additional periods of isolated to scattered showers and storms
  are possible Monday and Tuesday. At this time, Tuesday afternoon
  and evening holds the greatest potential to have a few strong
  to severe storms with gusty winds the primary hazard.

- Mostly dry conditions with slight improvements to the heat and
  humidity are expected mid to late week.

&&

.DISCUSSION...
Issued at 253 PM EDT Sat Jul 25 2026

A ridge axis remains centered well to our west while bouts of energy
will rotate through mean flow aloft this afternoon and tonight. This
will amplify troughing over the Mid-Atlantic into the southern
Appalachians. H85 and higher altitude flow will see minor
enhancements in response to the increasing vorticity advection
tonight. Because of this, the HREF suite depicts developing
scattered showers and storms across the region.

There will be a low risk of isolated flooding through the night.
Aspects of the atmosphere in favor of isolated flooding will be high
freezing-levels, anomalous PWATs, skinny CAPE profiles, and a few
locations that remain with poor antecedent soil conditions. Working
against the threat of isolated flooding is storm motion and lack of
a surface boundary to train along. Additionally, latest RAP and
NAMBufr soundings both depict a rather dry atmosphere at ~550mb and
higher, suggesting limited depth of saturation.

Sunday afternoon looks to be mostly dry, though an isolated shower
or storm cannot be totally ruled out. By Sunday night into early
Monday morning CAMs are suggest a MCS progressing through northern
KY and southward through portions of central and East Tennessee.
This activity moves quite quick so flooding should not be of
concern. The main focus will be keeping an eye on the potential for
some strong to damaging wind gusts. NAM soundings depict a fairly
stout low-level inversion so confidence is low that damaging gusts
could make it to the surface. Will have to keep an eye on how the
potential CAPE gradient plays out alongside timing trends.

A more potent shortwave is expected to promote development of an
upper low over the eastern Great Lakes and Mid-Atlantic Tuesday into
Wednesday. A surface low develops in response, and an associated
cold front will bring increasing chances for showers and storms.
NAMBufr soundings have quite an impressive thermodynamic profile at
least for Tuesday afternoon, but timing of the storms may not
necessarily work out to tap into peak heating and the latest hi-
resolution guidance does not quite make it into those overnight
hours. LREF joint probabilities of MUCAPE 1500+ J/kg and shear
30+kts are generally around 40 to 60% in our northeastern locations
where a day 4 Slight risk is currently in place. Primary hazard
would be damaging winds.

Regarding temperatures, Sunday through Tuesday will lean hot & humid.
Heat indices will be greatest Monday and Tuesday, with near to low
100 degree values expected to creep into the central valley. Post
FROPA, mostly dry and slightly cooler/less humid conditions are
expected mid to late week.

&&

.AVIATION...
(00Z TAFS)
Issued at 737 PM EDT Sat Jul 25 2026

Radar is quiet currently but activity is expected to pick up in
the overnight hours. Showers and possibly a few storms will be
isolated to scattered mainly from midnight until daybreak. MVFR
CIGs are likely at TRI and TYS late tonight through the morning
hours. Some fog is possible but dense fog is unlikely. Shower
activity is expected to be isolated tomorrow afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             73  91  72  93 /  60  20  20  30
Knoxville McGhee Tyson Airport, TN  71  88  71  90 /  80  30  30  30
Oak Ridge, TN                       70  88  70  90 /  80  20  20  30
Tri Cities Airport, TN              66  84  66  86 /  60  50  20  20

&&

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

$$

DISCUSSION...KRS
AVIATION...McD