431 
FXUS64 KMRX 121838
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
238 PM EDT Sat Sep 12 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 237 PM EDT Sat Sep 12 2026
 
- Scattered to numerous showers and thunderstorms across the area
  today, capable of some gusty winds and heavy rains. Some 
  localized flash flooding wouldn't be out of the question.

- A return to upper ridging aloft, and subsequent hot 
  temperatures, appears likely for this coming week.


&&

.DISCUSSION...
Issued at 237 PM EDT Sat Sep 12 2026

A shortwave trough will be moving from Middle Tennessee eastward 
through the southern Appalachians this afternoon into tonight. Ahead 
of this feature, widespread showers, with some embedded 
thunderstorms, are ongoing across the Cumberland plateau and the 
Tennessee valley. Do not believe there's much of a risk of any 
severe storms today, as instability is somewhat limited (MLCAPE 
values are on the order of about 1,500 J/kg). A couple of stronger 
storms capable of winds in the 40-50 mph range could occur, but 
overall the threat is limited I think. Additionally, PWATs are quite 
high (between 1.8 and 2.0" across our CWA) so heavy rains and some 
localized flooding issues could arise if there is any training of 
convection. This appears to be a limited threat as well, given 
storm motions, but worth keeping an eye on for sure.

The shortwave shifts east of the forecast area by late this evening 
and the overnight hours. We likely keep some lingering showers, 
especially in the northern mountains thanks to aided lift from 
increasingly upslope flow, into the morning hours on Sunday. But 
otherwise we should see increasingly dry conditions to finish out 
the weekend.

Afterwards, upper ridging builds back into the region, with little 
to no chance of rain outside of perhaps the East Tennessee 
mountains, and afternoon temperatures rising firmly back into the 
upper 80s to mid 90s by Tue/Wed of this coming week. 

We'll have to wait and see how the latter part of the week shapes 
up. Currently some deterministic guidance bring an upper low from 
off the southeast coastline, westward across northern Florida and 
into the Gulf. This would weaken the ridge and could lead to much 
better rain chances across the area. But suffice it to say the 
details would matter greatly, so for now the forecast just shows a 
gradual increase in rain chances towards the end of next week.

&&

.AVIATION...
(18Z TAFS)
Issued at 123 PM EDT Sat Sep 12 2026

SHRA with embedded TSRA are moving from the plateau into the 
central and northern TN valley this afternoon. High confidence 
these will impact KTYS so will go with a TEMPO there, but maintain
PROB30 for thunder elsewhere mainly due to timing uncertainties
and whether storms hold together. For tonight, guidance is mixed
on whether fog or low clouds form. HREF probabilities for fog/low
clouds is highest at KTRI so will include the lowest flight
categories there, with just MVFR VSBY at KTYS. KCHA should stay
VFR.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             70  94  70  95 /  20   0   0   0 
Knoxville McGhee Tyson Airport, TN  69  90  69  90 /  30  10   0   0 
Oak Ridge, TN                       68  90  68  90 /  20   0   0   0 
Tri Cities Airport, TN              66  85  65  84 /  50  10   0   0 

&&

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

$$

DISCUSSION...CD
AVIATION...CD


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