FXUS64 KMRX 181824
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
224 PM EDT Mon May 18 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 224 PM EDT Mon May 18 2026

- Very warm temperatures for Tuesday with highs 10 to 15 degrees 
  above nromal.

- Increasing chances for showers and storms return Wednesday.
  Scattered showers and thunderstorms are expected each day from
  Thursday through the weekend especially across the higher
  elevations.

&&

.DISCUSSION...
Issued at 224 PM EDT Mon May 18 2026

Main weather feature through Tuesday night will remain an upper 
ridge over the southeast United States into the southern 
Appalachians. Main impact will be mostly dry and unseasonably very 
warm temperatures. Highs will be 10 to 15 degrees above normal. Near 
record highs anticipated.

For Wednesday, ensemble cluster analysis shows a short-wave trough 
moved east of Great Lakes and upper Ohio valley. This wave will 
weaken the upper ridge over the region and allow a frontal boundary 
to approach the area. Lower heights and better PWs will allow for 
increasing chances of showers and thunderstorms especially over the 
Plateau counties. Instability with remain marginal with CAPES of 
1000-1500, mid-level lapse rates of 6 degrees or less with little to 
no shear. At this time severe storms are not anticipated.

For Thursday, frontal boundary remains near the region with PWs of 
1.5-1.7 inches so moisture returns over the area. Depending where 
frontal resides (GFS suggests across northeast Tennessee and 
southwest Virginia) that is where the highest chances of convection 
will be. Instability and shear remain limited with little to no 
severe threat, but fairly good coverage of showers and storms with 
much needed rainfall. QPF for Wednesday through Thursday will range 
from 0.10 to 0.50 inch.

For Friday, frontal boundary lifts north as an upper trough/jet 
moves northeast into the mid-west and Ohio valley producing pressure 
falls there. The increase in southerly boundary jet will pull 
frontal boundary north. Plenty of moisture and instability remains 
so scattered showers and thunderstorms developing into the afternoon 
especially across the terrain features. 

For Saturday through Monday, the southern Appalachians will remain 
with plenty of moisture and afternoon instability with an upper 
trough across the southern Plains. This upper trough will slowly 
move toward the Tennessee valley. Ensembles and deterministic models 
show better instability with possible short-waves ejecting out the 
trough across the region. There is a greater threat of stronger 
afternoon storms during this period.

&&

.AVIATION...
(18Z TAFS)
Issued at 108 PM EDT Mon May 18 2026

VFR conditions will prevail throughout the forecasts. Winds will
be gusty up to 20 kts possible this afternoon and Tuesday
afternoon. 

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             68  89  68  88 /   0  10  10  70 
Knoxville McGhee Tyson Airport, TN  67  90  68  88 /   0   0   0  30 
Oak Ridge, TN                       66  88  65  86 /   0   0  10  60 
Tri Cities Airport, TN              62  89  63  87 /   0   0   0  40 

&&

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

$$

DISCUSSION...DH
AVIATION...DH