885 
FXUS64 KMRX 181907
AFDMRX

Area Forecast Discussion
National Weather Service Morristown TN
307 PM EDT Sat Jul 18 2026

...New DISCUSSION...

.KEY MESSAGES...
Updated at 246 PM EDT Sat Jul 18 2026

- Daily chances of showers and storms continue through the 
  weekend. A few strong to marginally severe storms could produce 
  gusty winds and localized flooding.

- Muggy conditions with near normal temperatures continue through
  the early next week.

- Drier and cooler conditions expected for the latter half of next
  week. 

&&

.DISCUSSION...
Issued at 246 PM EDT Sat Jul 18 2026

This afternoon an upper level shortwave is translating south through 
the Canadian province of Ontario. The associated amplification of 
troughing across the Great Lakes and Ohio Valley will help flatten 
the southeastern CONUS ridging. Trends of the 12Z HREF members have 
been to keep this afternoon and evenings convective coverage more 
isolated to scattered. Latest radar trends suggest that we are 
somewhere between the most bullish and most passive models, with 
moreso weakly scattered coverage in vicinity of confluence and 
convergence at H85. 

Admittedly, confidence is on the lower side of how exactly the 
coverage of storms plays out this afternoon, largely due to poor mid-
level lapse rates thanks to an upper level high centered over the 
CWA. So far this high has done a pretty decent job at taming 
convection trying to sprout across the valley, with the best 
coverage near areas of higher terrain. Nonetheless, with 1500-2500 
J/kg MLCAPE a few strong to severe storms cannot be ruled out. With 
PWATs in the 90th percentile, some isolated flooding will be 
possible where multiple storms track over one location. 

A mostly quiet overnight is expected as a surface cold front begins 
to sink into the southern Ohio Valley. However, a few CAMs suggest 
some convection surviving along the previous evenings outflow and 
some folks, mainly north of I-40, could wake to a few rumbles of 
thunder and rain. Additional scattered showers and storms are 
expected to develop as the diffuse front works south into the 
afternoon and evening. Similar story in that you cannot rule out a 
few strong to marginally severe storms with localized flooding due 
to the anomalous moisture availability.

Best chance for additional precipitation in wake of the washing out 
front will be in the higher terrain and the very southern tier of 
counties. Long range guidance is still very bullish relative to the 
NAM now coming into range, and NBM probabilities may be weighted too 
high because of this. The next focus will be the potential for a few 
strong to severe storms in the Tuesday night to Wednesday timeframe. 
Timing still remains quite variable between deterministic models,
but overall, a more prominent shortwave is expected to dive into 
the upper trough and amplify low and mid-level flow. With 
increased shear profiles and a continued unstable airmass that 
strong to severe threat will persist. As it stands, the day 4/5 
convective outlooks sit on the CWA fringes. Post frontal passage, 
drier and cooler air move into the region for mid to late week.

&&

.AVIATION...
(18Z TAFS)
Issued at 149 PM EDT Sat Jul 18 2026

Another round with isolated to scattered afternoon showers and
storms. However, confidence in direct impacts to a terminal are
lower relative to yesterday due to the presence of an upper level
high centered over East TN. Tonight, a cold front will move into 
northern KY. A few showers and storms will be possible in the mid 
to late morning at TRI and maybe TYS associated with outflow. 
Included a mention of MVFR cigs at TRI with this activity. 
Additional afternoon convection tomorrow afternoon.

&&

.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN             73  91  73  91 /  10  60  20  50 
Knoxville McGhee Tyson Airport, TN  73  88  72  89 /  40  70  20  50 
Oak Ridge, TN                       72  88  72  89 /  30  80  30  50 
Tri Cities Airport, TN              69  84  68  87 /  60  70  40  50 

&&

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

$$

DISCUSSION...KRS
AVIATION...KRS


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