2000 Joules
Sunday, August 16, 2026 · 5:59 PM
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Dangerous heat is expected through Monday with triple digit heat indices across most of Middle Tennessee. This is resulting in major to extreme risk for heat-related illnesses. Please take the necessary precautions to protect yourself and loved ones from this oppressive heat. Medium storm chances on Monday may bring a damaging wind risk during the afternoon and evening hours, especially to areas east of Interstate sixty-five. Extreme heat and humidity should be out of Middle Tennessee by late week. Two hundred fifty millibar ridge! Stuck over the Great Smoky Mountains! Eleven zero seven A.M. Central Daylight Time! One hundred five—one hundred ten! Urban sprawl burning up! Seven P.M. tonight—expires! Immediately replaced— Heat Advisory through seven P.M. Monday! Lows in the upper seventies— No recovery—stuttering— Zero relief overnight! The flow moderates—zonal— One final headline! Sixteen twelve zulu High Resolution Ensemble Forecast! Surface based convective available potential energy! Two thousand joules per kilogram! Between four P.M. and eight P.M.! Lack of shear—does not matter! Strong forcing— Damaging wind gusts breaking through! Double! Edged! Sword! The Plateau collapses! Full sun! High humidity! Four P.M.! Eight P.M.! Forcing the front! Forcing it down! The ridge breaks apart! The front takes its toll! Four P.M. to eight P.M.! 2000 Joules! Below one hundred by Friday... First time in over a week... Zonal flow aloft... Breathing again... Breathing...
The forecast discussion
KEY MESSAGES
Updated at 550 PM CDT Sun Aug 16 2026
- Dangerous heat is expected through Monday with triple digit heat indices across most of Middle Tennessee.
This is resulting in major to extreme risk for heat-related illnesses.
Please take the necessary precautions to protect yourself and loved ones from this oppressive heat.
- Medium storm chances on Monday may bring a damaging wind risk during the afternoon and evening hours, especially to areas east of I-65.
- Extreme heat and humidity should be out of Middle TN by late week.
SHORT TERM
(Rest of today through Monday) Issued at 1107 AM CDT Sun Aug 16 2026
Another scorcher is underway across Middle TN. This morning's upper air flights depicted a large 250 mb ridge over the Great Smoky Mountains.
This is effectively creating a "heat dome" with subsidence trapping hot, moist air at the surface, resulting in dangerous heat indices for Middle TN. Expect another day of widespread heat indices above 105F today, maybe even hitting 110F in some areas with more urban sprawl.
As such, the Extreme Heat Warning is in effect through 7PM tonight.
Once that expires at 7PM, it will be immediately replaced by an areawide Heat Advisory through 7PM Monday.
We'll barely get any relief overnight tonight with lows in the upper 70s.
The upper level ridge will still be in place tomorrow, but gradually moderating back to more zonal flow, warranting one more day of heat headlines.
Tomorrow should be the last day of extreme heat for several days.
The cold front relieving us from the heat will be a double-edged sword tomorrow/Monday night.
It also brings a threat of severe weather to areas east of I-65. Instability will be plentiful under a day of full sun and humidity prior to the front's arrival.
The 16/12Z HREF suggests SBCAPE on the order of 2000 J/kg during the frontal passage between about 4PM and 8PM Monday.
While there is very little shear to hold everything together, a strongly unstable environment with a cold front moving through will still have the forcing needed to produce damaging wind gusts.
The bulk of the severe weather threat is over east Tennessee (where the best overlap of favorable ingredients is), but still expect to see a few hours of strong to severe storms mainly over the Plateau tomorrow afternoon and evening.
LONG TERM
(Monday Night through next Sunday) Issued at 1107 AM CDT Sun Aug 16 2026
Behind the front on Tuesday, temperatures and resultant heat indices take a dip back toward normal.
Keep in mind that it's still mid August, so "normal" is still hot, around 90 degrees.
This relief will be short-lived due to a warm front lifting across the state on Wednesday, bringing us right back up to borderline Heat Advisory criteria.
It's too early to make that call right now, but we may just skirt by without heat headlines on Wednesday.
The majority of the warm front's impact will be felt over West Tennessee with heat indices around 105 toward the TN River, but it will be close.
The pattern finally starts to mediate back toward climatological normals at the end of the week.
By Thursday, zonal flow aloft will help send heat and humidity well below headline thresholds.
By Friday, expect heat indices below 100 degrees areawide for the first time in over a week.
This cooler trend continues through next weekend.