637
FXUS64 KMRX 200522
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
122 AM EDT Sun Sep 20 2026

...New DISCUSSION, AVIATION...

.KEY MESSAGES...
Updated at 112 AM EDT Sun Sep 20 2026

- Well above normal temperatures to persist into early this week. But
  relief is on the way, with a pattern change expected mid-week
  and much cooler temperatures to follow.

- Expect isolated to scattered showers today, with increasing
  coverage Monday through Wednesday.

- A few strong to severe storm with damaging winds could occur
  today and Monday, with damaging winds being the primary threat.
  Localized flooding will be possible each day through Wednesday
  as well.


&&

.DISCUSSION...
Issued at 112 AM EDT Sun Sep 20 2026

An upper ridge, still centered over the Arklatex, will continue to
weaken on Sunday. Despite lowering heights, I would expect there to
be less shower and thunderstorm coverage today versus the last
couple of days thanks to a lack of forcing mechanism and slightly
lower low level moisture and PWATs. There will be convection, just
not as much. An isolated strong to severe storm and damaging wind
threat, or some localized heavy rains, can`t be ruled out. But, the
threat is quite low and I would expect that we will remain in the
general thunder area in SPC`s Day 1 convective outlook. For Monday,
expect a marked increase in convective activity as a weak upper low
shifts east from the plains into the Ohio valley. Forecast soundings
suggest afternoon MLCAPE values will range from around 1,500 J/kg to
over 2,000 J/kg area wide Monday afternoon. PWATs will increase a
bit too, all of which will support some isolated damaging wind gusts
from collapsing storms. Storm motions will be slow too, so localized
heavy rains and flooding could be an issue too. Tuesday should
feature fairly widespread showers too, but instability looks far
less so the severe potential looks negligible.

Lastly, despite the waning influence of the ridge, there`s no air
mass change until the mid-week time frame. So temperatures will
remain well above normal Sunday through Tuesday. Highs in the upper
80s to mid 90s are on tap for Sun and Mon, with low 80s to low 90s
for Tuesday. Barring any unforeseen circumstances, Chattanooga looks
to continue it`s record setting streak of 90 degree days and should
top out at 50. Wednesday is the first day of sub-90 forecast highs.

Speaking of Wednesday, and a break in the heat...late Tuesday into
Wednesday a rex block pattern sets up, with the upper ridge building
on the Canadian side of the Great Lakes, and the upper low
re-intensifying south of the ridge over the Ohio valley. This will
result in surface high pressure well to our north, and northerly low
level flow pushing a cold front through the region sometime on
Wednesday. We`ll still be warm...maybe 1-3 degrees above normal as
opposed to +12-15 degrees...but rain and cloudy conditions will be a
welcome change. We`ll wrap the week with temperatures around or
slightly below normal with highs in the 70s to 80s, and lows in the
50s may even make an appearance by week`s end.

&&

.AVIATION...
(06Z TAFS)
Issued at 112 AM EDT Sun Sep 20 2026

VFR throughout for TYS and CHA. For TRI, areas of fog likely to
develop overnight and dissipate after sunrise. Similar pattern
as the previous few days supports locally dense fog. IFR or worse
VSBY/CIGs likely. Isolated showers and thunderstorms possible
Sunday afternoon, coverage remains uncertain with TRI most likely
to see any RA/TSRA. Maintained PROB30 as a result. TYS and CHA
remain VFR with scattered afternoon Cu. Light and variable winds
throughout.


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             96  72  96  70 /  20  10  40  60
Knoxville McGhee Tyson Airport, TN  93  70  92  69 /  20  10  40  60
Oak Ridge, TN                       92  69  92  68 /  20  10  50  60
Tri Cities Airport, TN              88  66  88  65 /  40  10  50  50

&&

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

$$

DISCUSSION...CD
AVIATION...BH