It’s been a beautiful Wednesday across the Tennessee Valley! Skies have been mostly clear, and temperatures have been very comfortable today, with daytime highs in the lower 70s with low humidity. There have been more widespread clouds and showers off to our south over central Mississippi to south-central Alabama, but these are staying to our south for the time being.
Skies will stay clear for the overnight. Lows tonight will get down into the low to mid 40s across southern middle Tennessee and the mid to upper 40s across northwest Alabama and northeast Mississippi. Thursday will be a warmer day, with a southerly wind of 5 to 10 mph and mostly sunny skies leading to daytime highs in the mid to upper 70s.
Temperatures will stay on the warm side right on through the weekend, with highs in the 75-80 range for Thursday, Friday, and Sunday. We do step back to the lower 70s on Saturday with more in the way of cloud cover and scattered showers and a few non-severe storms around. Those warm temperatures and low rain chances through at least Friday will mean the pollen will continue to be out of hand, with no real relief coming until better rain chances over the weekend. Sunday looks mostly dry during the daytime, with the exception of a few isolated showers or thunderstorms during the afternoon.
It’s a broad period from the evening hours of Sunday, through the overnight, into the early morning hours of Monday that we will watch for the potential for strong to severe storms across the Tennessee Valley. We’re still a bit too far out for specific details, but we are starting to see signals for two threat regimes/times to emerge:
- A more uncertain threat during the evening hours of Sunday. There is the potential for a lead disturbance in the upper atmosphere to ride through the jet stream and help break the capping inversion across the area. The cap is a layer of warm air in the mid-levels of the atmosphere that keeps storms from forming. If that disturbance breaks, it would allow scattered storms to develop in the evening hours when the low-level jet is intensifying and there is still enough directional shear for rotating updrafts. This would allow for the potential for those scattered storms to become supercells with some degree of a tornado threat, in addition to wind and hail. We’re just not overly confident that the capping inversion will break. The lead disturbance that may do it is a subtle one instead of a large storm system like you’d expect in an outbreak. This means they’re harder to forecast in advance because very small changes to their exact timing, placement, and strength can cause big differences in the outcome. We will have a better handle on this potential as we head into Friday and Saturday and get the system into the higher resolution model data.
- The higher confidence situation, regardless of whether that conditional evening threat happens or not, is for the cold front itself to move in during the late overnight hours of Sunday into the early morning hours of Monday. This would cause a more widespread line of storms to move through, with the potential for some of the storms in the line to produce damaging straight-line winds and maybe a couple of spin-up type tornadoes… in addition to heavy rain and frequent lightning.
We will start to know more on exactly how this will play out as we work through the coming few days. Keep checking back for updates to the forecast as we figure out the specific details, and be sure to review your severe weather safety plans while the weather is quiet… and that means making sure you have multiple reliable ways of hearing warnings, including something that will wake you out of your sleep during the overnight hours!
