A swath of East and Middle Tennessee is starting the day under dense fog advisories, with visibility dropping to a quarter-mile or less in many spots. In the Cumberland Plateau region—including Cumberland, Pickett, and Fentress counties—the advisory began at 1 a.m. CST and continues through 9 a.m. Farther east, additional advisories went into effect at 6:15 a.m. EST for Morgan, Blount, Rhea, Meigs, Monroe, Roane, Bledsoe, Loudon, McMinn, and Anderson counties, also lasting until 9 a.m. Forecasters warn that the fog is thick enough to make travel difficult, especially along rural highways, valleys, and higher elevations where visibility can rapidly deteriorate. Portions of southwest North Carolina and southwest Virginia are experiencing similar conditions. Drivers are urged to slow down, keep headlights on, and allow extra space between vehicles until the fog lifts later this morning.