“Don’t like the weather in Tennessee? Wait five minutes.”
That’s the old adage for mother nature’s tendencies in the Volunteer State. And while, to be fair, it’s an adage that’s used by residents of at least half a dozen states and regions in the U.S., it’s being proven true in Tennessee this week.
After the month of July started abnormally dry and abnormally hot, the weather pattern has been turned on its nose with almost daily rounds of thunderstorms — and the trend looks to be towards even wetter weather as the final week of the month progresses.
The northern Cumberland Plateau’s relatively wet pattern began with a severe thunderstorm that impacted much of Scott County on July 21. That storm caused sporadic power outages that kept Plateau Electric crews busy for much of the night and caused a narrow swath of wind damage from Big Ridge Road to the east of Ponderosa Estates.
Monthly rainfall is still way below normal in Scott County. Even though nearly an inch of rain was recorded in Oneida with the July 21 thunderstorm, only 1.5 inches of rain have been received for the month — only a little more than one-third the normal amount of rain received in July. But if current weather forecasts prove true, the rain tally could move a lot closer to average by the time July exits Friday night.
Currently, the National Weather Service’s Morristown weather forecast office is calling for greater than 50% chances of thunderstorms each day for the rest of the week, with 80% rain chances on Thursday and Friday.
The culprit is a broad trough in the upper atmosphere over the eastern United States, a feature that generally leads to cooler temperatures and higher rain chances. A storm system over the Northeast promises to drag cooler air into the South, and that frontal boundary will serve as an additional aid for thunderstorm development. Following that, the trough will begin to lift and allow warmer air to flood into the region, which will serve as a catalyst for moisture to be transported northward from the Gulf of Mexico, leading for the even higher rain chances heading into the weekend.
Modeling data has shown precipitable water in the atmosphere ranging from two to 2.5 inches, which indicates a threat of moderate or even heavy rainfall. And although it’s impossible for meteorologists to pinpoint where the heaviest precipitation will set up when it’s associated with convective features like thunderstorms, some areas could receive as much as four inches of rain by Friday night. Flash flooding is possible later in the week wherever the stronger thunderstorms set up, but it’s impossible to project where that might be; during the summer thunderstorm season, there’s a broad line between the haves and have-nots when it comes to significant rains.
Meanwhile, there’s the potential for yet another cold front — somewhat of a rarity during the summer months — to invade the region by the end of next weekend.
In addition to the potential for excessive rainfall, another part of the equation is temperatures. After Oneida recorded seven consecutive days of temperatures in the 90s, the first time that had happened since June 2018, temperatures have settled back closer to normal. There’s even a chance for below-normal temperatures later in the week; the current NWS forecast depicts temperatures in Oneida struggling into the mid 80s on both Thursday and Friday, and staying in the low 80s through Monday, with the exception of Saturday, which has a forecasted high of 84.
The Climate Prediction Center, a division of NOAA, is forecasting below-average temperatures to persist in Tennessee through the next 14 days, but some models are showing the heat returning by the end of the first week of August.
As for the wet weather pattern, the CPC is forecasting wetter than normal conditions overall for Tennessee through the month of August and on into September.