We’re entering Day 2 of a two-day break between weather systems here across the Tennessee Valley, and that means active weather is on the way. Today is quiet, but we see rain and a few rumbles of thunder return later tonight into Saturday morning as the warm front lifts north across the area. We don’t expect any severe weather with this round of activity, but there could be some isolated flooding with heavier downpours. The main risk of severe storms and flash flooding will crank up over the area near and after sunset Saturday evening and continue into the overnight hours. There’s a lot to talk about. Let’s dive into it!
Severe Storm Threat:
The early morning outlook update from the NWS Storm Prediction Center has slightly expanded the Level 3 of 5 risk of severe storms for Saturday a little farther into northwest Alabama and northeast Mississippi. That “Enhanced Risk” now covers a large part of Franklin County, Alabama and Tishomingo County, Mississippi and into western portions of Colbert County, Alabama. The remainder of our viewing area across southern middle Tennessee and north Alabama remains in the standard Level 2 of 5 risk of severe storms. However, additional changes to the risk areas could be made as we get closer and new data becomes available.
We’ve been watching data to gauge the potential for a few individual supercell thunderstorms ahead of the main line during the late afternoon to early evening that would potentially have an elevated tornado threat IF they were to develop. We still can’t completely rule that out, but we have not seen a strong signal for it in the data in our local area. We think the core threat in our local viewing area will be with the main line of strong to severe storms ahead of the cold front, and this pushes the threat timing into the evening and overnight for us. With this main line of storms, the main hazards will be the potential for damaging straight-line winds with some areas possibly seeing wind gusts of 50-70 mph along the line, and the potential for heavy rain and flash flooding. However, there is also the threat of a few spin-up tornadoes within the line as well. Because of the saturated soil conditions and how that softens the ground and weakens the tree root systems, it will be even easier than usual for these winds to knock down trees and power lines across the area. An overall timeline map for the main line of storms is above, and you can click on it to make it larger. Please note that these wide time ranges on the map do not mean that it will storm that entire time at your location. We are starting out with a wider time window to give wiggle room for the line to trend slower or faster in the data, and then we will narrow these time ranges as we get closer. We do this so that you are not caught off guard if the line trends faster or if it trends slower. Instead of setting ourselves up to have to make a big change later, we are accounting for both potential scenarios now and then will tighten those times as we get more confidence in the specific timing.
Flash Flooding and River Flooding Threat:
The National Weather Service offices in Nashville and Memphis maintain a FLOOD WATCH across all of our Tennessee and north Mississippi counties from tonight through Sunday morning for the potential for flash flooding for more heavy rain as the storms move through. While that does not include north Alabama at the time of this writing, the Flood Watch could be expanded to include these areas in later updates. That decision will be made by the National Weather Service in Huntsville. The NWS Weather Prediction Center has shifted their higher-end “Moderate Risk” (Level 3 of 4) of excessive rainfall and flooding back northward out of most of our viewing area. In our 14-county viewing area, it now only includes areas north of a line from Savannah to Hohenwald to Spring Hill in Tennessee. The remainder of our area remains in the Level 2 of 4 risk of flooding, what we call “Possible” to make the risk levels easier to understand. While this isn’t a higher-end threat level, it doesn’t have to be. ALL of the flooding that happened across our area earlier this week happened under this very same risk level! We expect another 2 to 3.5 inches of rain to fall across our southern Tennessee counties and down into Lauderdale, Colbert, Franklin, and Limestone Counties of northwest Alabama. Southeast of there, we expect 1.5 to 2 inches for places like Moulton, Decatur, and Hartselle in north Alabama. Keep in mind, much of the area already saw between 3 and 5 inches of rain earlier this week. It’s not going to take much more at all to cause more flooding and flash flooding problems!
In addition to the flash flooding potential with the Saturday and Saturday night storms, there are already flooding conditions causing problems on some of the area rivers and lakes because of the heavy rain we’ve already had earlier in the week. A FLOOD WARNING remains in effect until early Saturday morning for Big Nance Creek near Courtland, AL. At 8:30 pm Thursday, the water stage was at 17.8 feet with bank-full stage being at 12.0 feet. Flooding is ongoing in these areas, with water levels cresting in moderate flood stage today before decreasing by Saturday. A FLOOD WARNING is also in effect for the Tennessee River near Savannah, TN “until further notice” for expected flooding conditions in the area beginning this weekend and lasting into next week. Flood stage is 360 feet in this area, and after climbing into flood stage tomorrow, water levels are expected to keep rising toward a crest of 376.7 feet by Thursday, February 20th. While a Flood Warning has not yet been issued for the Tennessee River at Florence, AL, forecast conditions are for water levels to climb into minor flood stage today and continue through the weekend into early next week before cresting in minor stage at 20.2 feet early on Tuesday morning. These conditions may cause it necessary for a Flood Advisory or Flood Warning to be issued here as well.
Safety and Preparedness:
It is important that you have your safety plan in place, knowing where you will shelter in the event a warning is issued Saturday night. These storms will be moving fast, and it will be after dark, and that means you won’t have much time to react. You also need multiple reliable ways of hearing warnings, including something that can alert you if you lose power and something that can wake you out of your sleep since this will be an overnight threat. If you are traveling Saturday night, in addition to being mindful of the severe storm threat, use extra caution near low-lying areas that often have flooding problems. Do not try to drive through a flooded out roadway. Turn around and find an alternate route. Flash flooding after dark is even more dangerous because you can’t see the condition of the road under the flood waters!
We will be right here to track the storms and provide live coverage as necessary as they move in Saturday night!
