Soggy today and for much of the week. Flooding and severe storm concerns by Tuesday PM.
It's been a wet Monday so far with waves of showers and a few embedded thunderstorms moving into the area. Some of the rain has been locally heavy down over north Alabama with some areas already not too far from an inch of rain. Skies continue to be cloudy areawide, and more showers are redeveloping back over north Mississippi that will continue to roll through the area. Temperatures for most of our area have been rain cooled into the lower 50s, but the Highway 412 corridor of Tennessee has been holding onto the upper 50s so far, with less rain up that way.
Temperatures will hold steady in the 50s for the rest of the day, with continued rain and a rumble of thunder at times. There may be additional rainfall as we head into the evening, but things begin to temporarily quiet down as we head after midnight. The warm front lifts through the area, and our area becomes more capped with time. This puts a lid on the rain and storm development during the predawn hours of Tuesday. We can't rule out some isolated showers though. As the rain becomes less widespread, the southerly wind is able to affect the temperatures more, and we may actually see temperatures warm closer to the lower 60s as we head toward daybreak on Tuesday. Warming back to at least the upper 50s looks likely.
As we head into Tuesday, the weather starts to get more impactful in a few ways. First off, the rain we've had today will add together with projected heavy rainfall totals from tomorrow afternoon into early Wednesday morning and increase the risk of flooding and flash flooding. Our various National Weather Service offices have already placed all of our Tennessee and north Alabama coverage counties in a FLOOD WATCH that is valid through Noon on Wednesday. A widespread 2 to 4 inches of rain is likely, especially over north Alabama, and there may be isolated heavier totals. The Weather Prediction Center office of the NWS has outlooked parts of north and northeast Alabama in a Significant Risk of excessive rainfall and flooding, and this may have to be expanded westward.
In addition to the potential for flooding, a few of the storms Tuesday afternoon and evening may be strong to possibly severe. It's not a high-end or widespread threat, but the threat is definitely there. The Storm Prediction Center maintains a Level 2 of 5 risk of severe storms across all of our area. The timeline for the strongest storms in our viewing area is roughly from around 3:00 PM through 9:00 PM. It is during this period that daytime heating and instability, combined with strong wind shear in the atmosphere and a disturbance moving through, may spark off a few individual supercell thunderstorms over our area. These storms would have the potential for damaging wind gusts of 60 mph, quarter size hail, and a tornado threat. While everyone in the viewing area needs to pay attention, the area that looks to have a somewhat greater potential of this looks to be our northwest Alabama and northeast Mississippi counties, maybe up to around Highway 64 in southern middle Tennessee. This is where the Storm Prediction Center is focusing their 5% tornado probability area in their outlook. Five percent doesn't sound like much at all because of how we view rain chances, but think about how much more likely you are to see rain on a particular day than you are to be directly hit by a tornado. The climatological average probability of a tornado within 25 miles of any spot in our area on any random February 22nd is 0.2%. That means that our area being outlooked in a 5% risk tomorrow shows that the risk in that area tomorrow is 25 times higher than it is on any other random February 22nd. Still, it's not a large-scale or high-end type threat, but even a single EF0 tornado or damaging wind gust is dangerous, and that's why you have to pay attention and be ready.
As we head into the midday and afternoon, southerly winds and maybe a few sun breaks will allow temperatures to warm into the lower to maybe even middle 70s in spots, and dewpoints to climb into the mid 60s. This allows the atmosphere to grow unstable. As we head deeper into the afternoon, this is when we will be watching for the potential for a few of these individual supercells to develop. These will continue into the evening before storms grow more widespread and the severe weather and tornado risk rolls over into a widespread heavy rain threat. After 9:00-10:00 PM, this may become more of a flooding threat as we head into the overnight.
The front gets pushed southward on Wednesday, and even though there will be rain chances around (especially heading back into the evening and overnight), we will temporarily be into cooler air. Afternoon highs only reach the upper 50s and lower 60s. Low pressure develops on the front on Thursday and it moves back north as a warm front, and we are back into the warmer air with temperatures in the upper 60s and lower 70s with another round of storms. However, this wave doesn't look as dynamic, and we don't see a risk of organized severe storms for Thursday right now. The final push of cooler air comes going into Friday as the front moves south and showers taper with time. Highs get knocked back into the mid to upper 40s from Friday into the weekend.