Storms less numerous today, Watching Sally in the Gulf, Cooler for the weekend?
After the widespread heavy rain and flooding on Sunday, things are a good bit calmer in the immediate Tennessee Valley area for this Monday. We are sitting between the washed-out frontal boundary just to our north and what will soon be Hurricane Sally to our south in the northern Gulf of Mexico. There is subsidence (sinking air aloft) around the outside of Sally. When combining this with northeasterly winds during the day trying to inch slightly drier air into the area from the north, it looks like rain chances across our immediate area today will remain very isolated. There may indeed be a thunderstorm or two, but those aforementioned conditions should lead to drier weather today for most people. It is going to be a bit breezy today with those northeasterly winds because of the pressure gradient between high pressure to the north and Sally to the south. Winds may be a sustained 10 to 15 mph for a large part of the day, and some gusts may get as high as 20 or even 25 mph. Afternoon highs will range from the lower 80s in our Tennessee counties to the mid or maybe even upper 80s in our Alabama counties and over into northeast Mississippi. With the breezy conditions in place, though, it won't feel too bad outside during the afternoon hours.
Tuesday, we begin to get back into deeper moisture as Sally moves onshore and gradually approaches inland areas of the Deep South. This, along with that remnant frontal boundary nearby, will mean an increase in the chance of scattered showers and thunderstorms. It's not going to rain all day by any means, but a good number of us may see a shower or thunderstorm at times on Tuesday. Because of the saturated conditions and widespread flooding on Sunday, we will have to carefully watch for any localized heavy rain across our area. Any periods of heavy rain may increase the potential for localized flooding, at least on an isolated basis.
As we head into Wednesday and Thursday, our attention quickly shifts to what will soon be Hurricane Sally. Sally has been getting increasingly organized Sunday night into Monday morning, and this increasing organization has led to a trend for the system to have a more rightward/easterly track on its approach to the Gulf Coast and after landfall. The National Hurricane Center, as of overnight Sunday night, as the center of Sally tracking from southeast Mississippi to east-central Alabama from Wednesday evening through Thursday evening. The exact specific track of Sally will determine what kind of impacts we will have in our area, but a track like this with the center of circulation being south would be better for our viewing area. This would keep the heavier rain across central to east/northeast Alabama and southward and would keep the tornado risk completely south of our viewing area. While we can't completely rule out a shift back to the left/west, it is looking increasingly unlikely with time as Sally gets better organized and a better-organized storm would tend to turn more north and then easterly faster because of both the steering currents in place and the general Coriolis force and its tendency to lead stronger systems to turn more poleward than weaker systems. Generally speaking, even with this more easterly track, our area may still see as much as 1-2" of rain Wednesday night through Thursday night as Sally gradually moves through Alabama. We will have to watch for any westward shifts. Areas closer to the center of circulation may see 4+ inches of rain, and any westward shifts, even though they look unlikely now, would bring those higher rain totals closer to us and increase the threat of flooding in our viewing area. We will be watching carefully, even though that looks unlikely for now.
As Sally moves off to the east Thursday night and especially Friday, high pressure noses in from the north and gradually pushes drier and slightly cooler air into the region in the form of a weak cold front. Clouds decrease on Friday, and we eventually go partly cloudy to mostly sunny for the coming weekend and early next week. With the air mass change in place, high temperatures drop from the 80s into the mid to upper 70s and overnight lows for the weekend get down to the lower 60s. That continues into early next week where even the Euro, the model that's handled the slower timing of cooler air moving in so far this month, suggests that overnight lows for early next week might be as low as the mid 50s across the area!