114 
FXUS64 KMRX 191057
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
657 AM EDT Sat Sep 19 2026

...New AVIATION...

.KEY MESSAGES...
Updated at 653 AM EDT Sat Sep 19 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 142 AM EDT Sat Sep 19 2026

Saturday and Sunday will feature decreasing heights aloft as the 
upper ridge, centered over the Arklatex region, begins to break 
down. That will place thee southern Appalachian region on the 
periphery of the retreating ridge, allowing for a mix of diurnally 
forced convection and thunderstorm complexes moving in from the 
northwest in this "Ring of Fire" type setup. Much of the CWA is in a 
Marginal risk area for a damaging wind threat tomorrow, while only 
in a general thunder area on SPC's Day 3 outlook. I wouldn't be 
surprised to see that expanded on Sunday. The thermodynamic setup 
for both Saturday and Sunday looks similar to today, that is to say 
DCAPE values in the 1,000 - 1,200 J/kg range, favorable lapse rates, 
and MLCAPE north of 1,500 J/kg. As such, it would not be hard to 
imagine a scenario where a handful of Sig Wx Advisories and a maybe 
a couple of severe thunderstorm warnings are issued. 

Looking ahead to Monday and Tuesday, afternoon showers and storms 
remain in the forecast as the ridge continues to break down and an 
upper low, once over the Intermountain West, shifts east across the 
plains and into the Great Lakes region Sunday through Tuesday. 
Temperatures will remain well above normal through this time.

Tuesday night into Wednesday the upper low deepens over the Great 
Lakes region and leads to a pattern change characterized by much 
more notable troughing over the eastern CONUS as opposed to high 
pressure. In fact, we may have a legitimate cold front passage next 
Wednesday beneath the upper trough/low. In addition to increased 
chances for showers and storms this pattern will bring, 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 day where the official forecast is below 90 is 
next Wednesday. If they hold on to 90 through Tuesday, that would 
bring the streak up to 50 days.

&&

.AVIATION...
(12Z TAFS)
Issued at 653 AM EDT Sat Sep 19 2026

Areas of fog have developed across SW VA and NE TN early this
morning. This has led to IFR to LIFR vsby and cigs at TRI.
Conditions should improve quickly after sunrise with a return to
VFR between 13-14Z. For TYS and CHA, VFR to start the period with
only a few high clouds. I have included a PROB30 for -TSRA at both 
TYS and TRI this afternoon. Hi-res models show scattered
thunderstorms developing in the early afternoon hours and
dissipating by sunset. Confidence is not high enough to include
CHA in the PROB30 so opted to keep it dry for now. 


&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             98  72  96  71 /  30  10  30  10 
Knoxville McGhee Tyson Airport, TN  94  70  92  69 /  20  10  20  10 
Oak Ridge, TN                       93  69  92  68 /  30  10  30  10 
Tri Cities Airport, TN              88  66  86  65 /  20  20  40  30 

&&

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

$$

DISCUSSION...CD
AVIATION...BH


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