Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
889 FXUS64 KMRX 181200 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 800 AM EDT Tue Aug 18 2026 ...New AVIATION... .KEY MESSAGES... Updated at 741 AM EDT Tue Aug 18 2026 - Regular warm to hot August temperatures to continue, with on and off rain and thunderstorm chances returning Thursday and continuing into the weekend. && .DISCUSSION... Issued at 144 AM EDT Tue Aug 18 2026 We will see some minor relief next two days, with a return to typical summertime temperatures and a drop in the overall PWAT for the atmosphere. PWATs drop down to 1.2" or so, which is just above the 25th percentile for August, a time of year in which we`re at the climatological maximum for vertical water content. Since the upper heights are otherwise fairly flat, we only return to near or slightly above typical highs for August, so not sure how much jumping for joy our anti-humidity cabal will be doing this week. We will also likely remain dry the next two days, with surface ridging overhead and no obvious discernible source of forcing to get us storm development. Unfortunately we get another shortwave to arrive on Thursday, which has the side effect of re-introducing more rain and storm chances to our region, with higher chances in the north. 30 to 40 knots of shear exist Thursday into Thursday night, GFS and long range RRFS both depict a dying storm cluster early on Thursday to our west, then a lull likely from cloud debris, then potential for scattered PM and late night thunderstorms. Whether or not that scenario comes to fruition is an unknown. CAPE is a bit of a question, though depending on how the morning goes we may realize more CAPE than the low-biased GFS depicts. Shear profiles are more favorable for strong winds. Something to watch, anyways. Scattered rain and storms then will likely remain in the forecast into the weekend, as a series of shortwaves occur before a large trough digs into the Great Lakes and then the northeastern US Sunday into Monday. && .AVIATION... (12Z TAFS) Issued at 741 AM EDT Tue Aug 18 2026 Low CIG and BR impacting the terminals this morning. Models depict CIG lifting with time this morning. Once we improve to VFR, dry weather is on tap today under strengthening high pressure. Isolated activity could mainly impact nearest TRI, but confidence too low to include in TAF. Clearing and calm overnight tonight with possible CIG and VSBY to watch for again, but most likely not as bad as this morning. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 93 69 96 72 / 0 0 0 20 Knoxville McGhee Tyson Airport, TN 89 68 91 69 / 10 0 0 20 Oak Ridge, TN 89 66 91 70 / 10 0 0 20 Tri Cities Airport, TN 86 64 88 66 / 20 0 0 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...Wellington AVIATION...KS