Marine Weather and Tide Forecast for Knoxville, TN

DISCUSSION
Issued at 128 AM EDT Mon May 18 2026

Main weather feature for Monday and Tuesday 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.

For Wednesday, ensemble cluster analysis shows a short-wave trough moving across the Great Lakes and upper Ohio valley. This wave will begin to weaken the upper ridge over the region and allow a frontal boundary to approach the area. Surface ridging will also weaken across the southeast United States allowing for slightly better moisture return. 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. 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 and Sunday, the southern Appalachians will remain with plenty of moisture and afternoon instability with upper ridge building back into the region. More typical warm and muggy conditions are expected.

Ensemble QPF and WPC depicts from 1 to 1.5 inches across much of the area from Wednesday through the weekend.

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 67 89 66 87 / 0 10 10 70 Knoxville McGhee Tyson Airport, TN 66 90 67 87 / 0 0 10 70 Oak Ridge, TN 65 88 64 86 / 0 0 10 80 Tri Cities Airport, TN 62 88 63 86 / 0 0 0 70

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