Scattered storms today, Showers from Sally, Cooler to end the week
Not everybody will see rain on Tuesday, but we expect scattered showers and thunderstorms to be a bit more prevalent across the Tennessee Valley than they were on Monday. This will be partly in response to the deeper moisture associated with Sally moving back northward into the area as well as the squeeze play across the area between Sally and high pressure and a remnant frontal boundary north of the area. Most locations will see under a half-inch of rain today (and some locations may not see any at all), but there may be a few localized downpours where an isolated community or two may see over an inch of rain. The air will have a lot of moisture content; so, where it does rain today, it may be locally heavy for a short time. Aside from rain chances, clouds will be on the increase through the day as Hurricane Sally gradually approaches the northern Gulf Coast. While the afternoon showers will fade a few hours after sunset, those clouds will continuously get thicker overnight tonight.
Our attention shifts completely to Hurricane Sally as we head into Wednesday, with landfall along the northern Gulf Coast likely on Wednesday morning. Sally will then track east-northeast through south-central Alabama through Wednesday and a large part of Thursday before exiting into Georgia Thursday night. The latest forecast guidance, as the official track from the National Hurricane Center, has shifted even more to the south/east with the track now near or even slightly south of Montgomery as of the time of this predawn blog post. That more easterly track will mean the risk of severe weather and flooding from Sally will stay off to the south of our viewing area, with those impacts being highest south of I-20 in Alabama. I-20 is the interstate that runs from Tuscaloosa to Birmingham to Anniston. We may even get to shift that northern edge even more to the south with time. Having said that, we do expect a few scattered showers at times from Wednesday during the daytime through maybe Thursday evening or early Friday morning. Rainfall in our immediate viewing area won't be that heavy though, and it's very possible that the higher rain totals in our coverage counties will come from the scattered thunderstorms today and NOT from Sally on Wednesday into Thursday!
High pressure builds southward behind Sally as we head into Friday, and that pushes a cold front into the area. Much drier and somewhat cooler air will follow, and this will drop our afternoon highs from Friday into the weekend back into the mid-70s. There might even be a couple of days in there where we only get into the lower 70s, especially in our Tennessee counties. Overnight lows will also step solidly down into the 50s from Friday night into at least early next week. While I'm not yet ready to go as cool as some of these projected overnight lows from the GFS ensembles, our forecast isn't too far off, and we may have to drop our numbers a little closer to this as we get closer to the weekend and confidence increases. This is definitely a good shot of early fall weather, and it will be coming right on time, with the official start to astronomical fall being next Tuesday.