769 
FXUS64 KMRX 191818
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
218 PM EDT Sat Sep 19 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 217 PM EDT Sat Sep 19 2026

- Well above normal temperatures to persist into early next week.

- Expect isolated to scattered showers and storms each afternoon 
  today through Monday, then chances for showers and storms will 
  be higher Tuesday and Wednesday. 

- A few storms may be strong to severe with damaging winds the 
  primary threat each afternoon today through at least Monday. 
  Localized flooding will be possible each day through Wednesday 
  as well. 

- Cooler conditions are expected to arrive by the latter half of 
  the coming week. 

&&

.DISCUSSION...
Issued at 217 PM EDT Sat Sep 19 2026

The upper ridge that has been sponsoring our recent hot and mostly 
dry weather is centered off to our west and will be gradually 
breaking down through the remainder of the weekend into the early 
part of the week, with heights over our area showing a gradual 
decreasing trend. It remains quite hot this afternoon, with heat 
index values not far either side of 100 across many southern and 
central valley locations. We will see continue to see isolated to
scattered showers and storms around this afternoon and evening. 
The atmosphere today features minimal shear, but moderate 
instability, high PWAT values, steep low level lapse rates and 
DCAPE values either side of 1000 J/kg suggest an environment in 
which a few of the stronger storms could produce damaging winds. 

Models generally show a bit less coverage of storms Sunday afternoon 
with an uptick in coverage on Monday, but overall soundings do not 
look much different from today and we will continue to see the 
threat of a few storms becoming strong to severe with damaging winds 
the primary threat. PWAT values will remain high as well, so locally 
heavy rainfall will be possible with a threat of localized flooding. 
It will also continue to be quite hot for this time of year both 
days.

An upper low near the western Great Lakes region will move east and 
southeast during the mid week period, and a cold front will move 
through our area sometime around Wednesday. We will see an increase 
in showers and storms Tuesday and Wednesday, along with a moderating 
trend in temperatures as the heat loses its grip on the area.  

We will be in northwest flow aloft for the latter periods of the 
forecast with upper ridging to our west and a trough centered to our 
east. We may still have a few showers and storms around, but overall 
Thursday through Saturday should be drier and cooler. High 
temperatures are expected to be near to a bit below normal all three 
days. 

Lastly, until the expected relief from the heat arrives, Chattanooga 
will continue to build onto their record streak of 90 degrees or 
higher. They have climbed above 90 again today so they currently sit 
at 47 days, with a few more days likely to add to the streak. The 
first day where the official forecast is below 90 is Wednesday. If 
they hold on to the 90+ streak through Tuesday, that would bring the 
total up to 50 days.

&&

.AVIATION...
(18Z TAFS)
Issued at 1232 PM EDT Sat Sep 19 2026

Isolated to scattered showers and storms will be around this
afternoon, and will include prob30 thunder groups all three 
sites. The other concern will be possible fog development tonight
mainly TRI. If rain occurs at TRI this afternoon/early evening then
the chances for significant fog will increase, but that is still
unknown at this time. For now will add several hours of MVFR fog 
late tonight at TRI, but dense fog is a possibility again.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             72  96  72  96 /  10  20  10  40 
Knoxville McGhee Tyson Airport, TN  70  93  70  92 /  20  20  10  40 
Oak Ridge, TN                       70  92  69  92 /  20  20  10  50 
Tri Cities Airport, TN              66  88  66  88 /  30  40  10  50 

&&

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

$$

DISCUSSION...99
AVIATION...99


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