Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
182 FXUS64 KMRX 181752 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 152 PM EDT Tue Aug 18 2026 ...New DISCUSSION, AVIATION... .KEY MESSAGES... Updated at 148 PM EDT Tue Aug 18 2026 - Dry weather continues through tomorrow, then an approaching front will bring showers and storms on Thursday afternoon/evening, a few of which could be strong to severe. Rain chances continue into Friday with the frontal passage. - Mostly dry conditions with near normal temperatures through the weekend and early next week && .DISCUSSION... Issued at 148 PM EDT Tue Aug 18 2026 Today has been a welcome break from the hot and wet weather of the past several days, thanks to surface high pressure settling over the area and a dry W-NW flow through the column. This pattern continues through Wednesday as the track of MCSs will be along and north of the OH River. One concern for tonight is fog development, which could be dense and extensive if LAMP guidance pans out. Our temperatures have been a little cooler today, but dewpoints are still in the upper 60s to mid 70s in most spots and will likely remain there tonight. With the surface high remaining over the area and clear skies, it seems like a good bet to see widespread dense fog in the early morning. On Thursday, the cold front that will be the focus for shower/storms in the lower OH Valley on Wednesday will push southeastward in response to a deepening trough over the eastern Conus. The timing of this front remains uncertain, which will affect how extensive and intense the showers/storms will be in our area ahead of it. NAM forecast soundings show plenty of MLCAPE in place by the afternoon, 3000-4000 J/kg, with decent lapse rates up to 600 mb. There is some unidirectional shear as well with the midlevel flow around 30-40 kt. This suggests some potential for damaging winds, and maybe some hail, if timing is favorable. We are not currently in the Day 3 Outlook for severe, but if the NAM`s depiction holds, that could change. With the upper trough axis moving through and the surface front potentially somewhere near the area on Friday, the chance of showers will continue, mainly in the eastern half. The front will be east of the area on Saturday, bringing a drier air mass to the area for the weekend. The upper trough will still be over the area, so a few showers can`t be ruled out, but most of the area should remain dry. A NW flow remains in place through the first half of next week with the strong ridge over the southern Plains and a trough over the East Coast, which will favor dry conditions and near normal temperatures through Thursday. && .AVIATION... (18Z TAFS) Issued at 148 PM EDT Tue Aug 18 2026 Fog is the main concern for aviation tonight and tomorrow morning. Conditions appear favorable for fog, and model guidance is pointing in that direction. Will have vis going down to IFR at TRI, but lower conditions are possible. Will have TYS in the MVFR range for now, with no fog at CHA where daytime temperatures are higher and dewpoints have dropped with mixing. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 69 95 72 94 / 0 0 20 30 Knoxville McGhee Tyson Airport, TN 68 91 70 91 / 0 0 20 20 Oak Ridge, TN 66 90 70 89 / 0 0 30 40 Tri Cities Airport, TN 64 87 66 86 / 10 0 30 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...DGS AVIATION...DGS