Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
141 FXUS64 KMRX 221100 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 700 AM EDT Fri Aug 22 2025 ...New AVIATION... .DISCUSSION... Issued at 142 AM EDT Fri Aug 22 2025 Key Messages: 1. Scattered storms are possible across southern portions of the area and across the higher terrain today. More area-wide coverage is expected on Saturday and Sunday. 2. A significant pattern change is expected Monday through the week with highs into the 70s and lows dropping well into the 50s for many. Discussion: Currently, a ridge is centered over the Rockies with Hurricane Erin progressing northeast further into the Atlantic. A fairly stationary frontal boundary is to our south. With ridging remaining to our west, PWATs around 1.25 to 1.5 inches, and MLCAPE reaching around 1,500 J/kg, diurnal convection is anticipated today. With the better moisture in the south, the best coverage will likely be in southeast Tennessee, southwest North Carolina, and along the higher terrain. Low-end threats for flooding and strong winds remain, but many areas are likely to stay dry. Throughout the day, a deepening trough from Canada and increasing frontogenesis in the northern Great Plains will be of increasing focus. On Saturday, shortwave troughing will approach from our north with the aforementioned front moving into the central Great Plains. With even better moisture and comparable instability, diurnal convection is anticipated again but with better coverage than today. On Sunday, troughing will deepen and become more broad across the eastern U.S. with the front expected to move through the area overnight. This will support scattered to numerous convection moreso than Saturday. Winds aloft will remain weak but with potentially better mid-level lapse rates and instability. Still, the overall threat for severe storms is limited, but locally strong wind gusts and isolated flooding remain possible. Low probability HWO wording will be maintained. The front will be past the region by Monday with deepening troughing and approaching Canadian high pressure in the first half of the week. This will bring the long-anticipated pattern shift with drier and cooler conditions. By Tuesday/Wednesday, 850mb temperatures reach early October normals of 10 Celsius or lower with radiational cooling expected overnight into the morning. Based on these trends, widespread highs in the 70s and lows well into the 50s are very likely. Continued shortwaves will keep temperatures moderated through Thursday. && .AVIATION... (12Z TAFS) Issued at 507 AM EDT Fri Aug 22 2025 There will be some lower clouds around early in the period and again late, but right now the probability for MVFR cigs looks the most significant at CHA late in the period. Fog development late in the period is also possible especially TRI, but the chance looks too low to include for now. There will be scattered showers and thunderstorms around especially south during the afternoon, so will include a prob30 thunder group at both CHA and TYS. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 87 70 85 70 / 60 30 80 40 Knoxville McGhee Tyson Airport, TN 88 70 86 70 / 40 20 70 60 Oak Ridge, TN 89 69 85 69 / 40 20 80 60 Tri Cities Airport, TN 86 66 84 66 / 30 10 60 60 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...BW AVIATION...