Our next rain and storm chance arrives tonight and Wednesday. Temps not as hot this week.
All is quiet across the Tennessee Valley early on this Tuesday morning. The stalled frontal boundary that brought the weekend storms is still located down along the Gulf Coast, and the next front is still over the Ohio Valley and Mid Mississippi Valley. We are sandwiched in between, and for now, rain and storms are avoiding our immediate area. Temperatures as of the 2:00 AM hour tis morning range from the upper 60s to the lower 70s, and most of us should drop to around 66-72 degrees by daybreak. There had been some concern for patchy fog this morning near the lakes and rivers, but so far, that is staying off to our east. However, I can't rule out some isolated fog near those water bodies over the next few hours.
Our weather is mostly quiet again today. We look to stay mostly sunny through the morning with clouds increasing a bit during the afternoon. We look to be hot once again today, with afternoon highs in the low to mid 90s everywhere. Heat index values look to reach near the lower 100s, but won't be nearly as outlandish as anything we saw last week. I can't rule out a stray storm or two reaching the area as early as 5:00-6:00 PM, but most all of us should be dry for the daytime hours.
The chance for scattered showers and thunderstorms will make a return to the forecast for tonight and Wednesday. However, even this close to the event, there are still some questions about the overall timing of everything and also how the rain and storms will evolve. We're into that time of year where exactly how rain chances will play out is determined much more by how things evolve the night before or evolve way upstream, and the inner mechanics of the storms themselves... instead of things like organized frontal boundaries, jet stream dynamics, and easy-to-track features like that. That makes even higher rain chance days a bit harder to figure out and susceptible to forecast changes, even as little as 12 to 24 hours out.
We will start off with the high resolution Futurecast model from Baron. This latest run of the Baron Futurecast has a few isolated thunderstorms approaching our middle Tennessee counties during the evening, before fading out overnight as they try to move in, with them never fully making it through the viewing area. Then, there is a lull during the morning before scattered thunderstorm redevelopment by midday and afternoon on Wednesday, mainly over north Alabama. A shower or storm couldn't be ruled out Wednesday over Tennessee in this scenario, but the chances would be much lower.
Next is the HRRR model. This is another high resolution model we have available, this one run by NOAA. This is one of the main high-resolution convective models, and it also agrees with some of the other NOAA/NWS/NCEP models out there. This model shows thunderstorms a bit more widespread during the evening and overnight, with rain chances pretty elevated tonight for our middle Tennessee and northwest Alabama areas (especially near and north of the Tennessee River). This has multiple rounds of scattered showers and storms during the overnight hours tonight into the predawn hours of Wednesday morning, before a lull in the action during the daytime morning hours. Then, by midday and afternoon, the HRRR model also shows redevelopment of showers and storms with a focus on the Alabama side of the state line. This model solution also agrees with the idea of lower (but not zero) rain chances over Tennessee on Wednesday, but it increases the chances of rain tonight areawide.
As showers work through the area both this evening/tonight and again on Wednesday, a few of them may be strong with the main concern being gusty winds. The overall threat is low, but we can't rule out a severe thunderstorm warning or two for straight-line winds or maybe even isolated small hail. Cloud-to-ground lightning and locally heavy rain will also be a main feature of any storms in the area.
An isolated shower or storm may linger into Thursday, but the deeper moisture will be temporarily shifting south of the area. That continues through Friday before it moves back north over the weekend. An isolated storm will be possible on Saturday before rain chances start to climb a bit Sunday and even more so into early next week.
Temperatures for the remainder of the week and into the weekend look to stay near the upper 80s and lower 90s for daytime highs, with morning lows between the mid 60s and lower 70s. Heat index values after today look to remain under 100 degrees through the weekend. This break from the hotter weather we saw last week is because the big upper ridge has shifted out into the western United States. That looks to continue into the weekend, but there are signs that ridging from the Atlantic may try to build back into the Southeast by early to mid next week. That remains to be seen, but it would bring hotter temperatures with it if that does happen.
The tropical Atlantic, for the most part, is quiet. However, we continue to watch the weak disturbance over the northern Gulf of Mexico. This is tied to the stalled frontal boundary that brought our storms back on Saturday. IF a low pressure can sustain itself over the open water for long enough this week, there is some chance that a tropical depression may develop. The National Hurricane Center gives the system a 30% chance of doing that over the next 5 days. Regardless of whether the system is able to do that, the main impact would be increased rain chances along the Gulf Coast, with rounds of widespread showers and thunderstorms being likely along and near the coastal areas this week.