Record-breaking heat to come to a halt, fall colors in limbo

Abnormally high temperatures in Tennessee caused by a heat dome are expected to drop this week, according to U.S. National Weather Service forecasts. A heat dome occurs when hot air expands resulting in a warmer atmosphere and higher temperatures. Meteorologist Matt Reagan at the NWS Nashville office said the timeframe of a heat dome depends on the upper air patterns. "We had a big area of high pressure that sat right over Tennessee," he said. "And there were no other upper air features that were present to kind of push that ridge or that dome of high pressure away from the area, so it sat there for multiple days." Heat domes are not uncommon and are often seen during the summer months, Reagan explained. "This one was particularly strong," he said. "We've been dry and that allows the air to heat up faster, as opposed to if you have more moisture… so if you have a dry air mass, dry soils allows temperatures to heat up much quicker than they would in August or July when there's more humidity." A cold front currently over Kentucky into far Western Tennessee, Reagan said, is expected to push through the state over the next couple of days, weakening the heat dome and bringing temperatures down. In Northeast Tennessee, temperatures are expected to drop into the 70s by Thursday and into the weekend with some chance of showers. Reagan said temperatures may rise again into the 80s following the cold front, but "just because you see above normal temperatures favored in that eight to 14 day period doesn't necessarily mean we're going back to this extremely oppressive heat." Meteorologist Sam Roberts, at NWS Morristown office, said last year the hottest temperature in the region for October was 83 degrees and in the past years it has been in the same range. Roberts said he advises people to take the same precautions they would during the summer months during these hotter days to keep hydrated and healthy. How does this affect the fall season? The first day of astronomical fall is Tuesday, Roberts said, but meteorologist fall was Sept. 1. He said astronomical fall is determined by how close Earth is to the sun. Reagan said the high temperatures this late in the year across the state will affect the colors of leaves that are typically seen during the season. "The hot, dry weather probably won't delay [the season]," he said. "It may actually kind of stop the colors. Instead of the reds and the oranges it just may go brown just from the lack of water and extreme heat." The heat dome, however, has not affected the migration of birds, he said, adding birds are already migrating and can be seen on the NWS radar, especially throughout the night.