859
FXUS64 KMRX 181840
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
240 PM EDT Fri Sep 18 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 238 PM EDT Fri Sep 18 2026

- Well above normal temperatures to persist through early next
  week. Heat Indices will remain in the upper 90s to lower 100s
  across the central east TN and southern TN valley through
  Monday.

- Temps cooling towards normal at the end of the forecast period,
  mid to late next week.

- Increasing rain chances this weekend into next week, similar to
  a typical summer pattern. Better chances for more widespread
  rain by Tue/Wed.

&&

.DISCUSSION...
Issued at 238 PM EDT Fri Sep 18 2026

Isolated showers and storms are currently ongoing across the area
and will persist until around 10 PM tonight. No severe weather is
expected. Any areas that see a decent amount of rainfall today will
likely see fog tonight.

Tomorrow, showers and storms are once again expected during the
afternoon and evening hours, but coverage should be a little greater
than today. This is due to the positioning of the high for tomorrow,
which will be just west of our area. This puts us on the eastern
periphery which means we will be in "Ring Of Fire" so to speak.
Basically meaning, greater chances for showers and storms due to
weak impulses moving through the northerly flow and into our area.
We remain in a marginal risk for severe weather for tomorrow from
SPC. The greatest threat will be damaging winds, possible straight
line and/or downburst. The wind threat is due to good low-level
lapse rates of around 7 to 8 deg C/km, DCAPE of around 1000 to 1200
J/kg, and drier air at surface which shows up in the soundings as an
inverted V. Storms will likely begin to develop between 1 and 2 PM
and dissipate by 10 PM. Again, a few strong to severe storms are
possible.

For Sunday, almost the exact same setup as Saturday, though perhaps
a little less coverage of showers and storms. SPC only has our area
in the general thunder outlook but I wouldn`t be surprised to see us
upgraded to a marginal.

For Monday and Tuesday, showers and storms remain in the forecast as
the ridge shifts further west and the flow becomes more zonal. A
more zonal flow provides better chances for at least some isolated
convection, less subsidence. Temps and heat indices remain elevated.

Tuesday night into Wednesday, an upper trough is set to swing
through the area. In addition to increased chances for showers and
storms, temperatures will begin cooling off behind on the backside
of the trough. Drier and cooler conditions expected on Thursday and
Friday. High temperatures will be in the 70s/80s as opposed to the
80s/90s. Overnight lows will be in the 50s/60s instead of the
60s/70s. So hold on for a few more days of heat, relief is on the
way!

Lastly, until we see a relief in temps, Chattanooga will continue to
build onto their record streak of 90 degrees or higher. They
currently sit at 45 days, with several more days likely to add to
the streak. The first official day where the forecast is below 90 is
next Wednesday, which a high of 87.



&&

.AVIATION...
(18Z TAFS)
Issued at 142 PM EDT Fri Sep 18 2026

Scattered small showers and a few skinny TS are developing right
now on satellite/radar. This activity will generally both
continue, expand in coverage, and move slowly to the south with
time. A low chance exists at all three TAF sites for a direct
terminal impact with brief rain and wind, but TYS has the greater
odds over the next couple of hours. Will monitor for additional
amendments.

Tonight, depending on the degree of moisture and outcomes from
current storms, patchy fog is going to form again over much of the
area. Included a restricted MVFR vis for now at TRI, but could see
fog similar to this morning between 08z and 1230z tomorrow
morning. Patchy fog, but lesser chances at TYS.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             74  98  72  96 /  10  40  20  30
Knoxville McGhee Tyson Airport, TN  71  94  70  92 /  20  30  20  30
Oak Ridge, TN                       70  93  70  92 /  20  30  10  20
Tri Cities Airport, TN              67  88  66  87 /  40  30  20  50

&&

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

$$

DISCUSSION...99
AVIATION...Wellington