The first round of storms we are watching for this week will move in later this morning. During the morning and midday hours, we expect a band of rain and embedded thunderstorms to work into the area from west to east. Locally heavy rain, some lightning, and gusty winds of maybe up to 30-40 mph in one or two places seems to be the main threats through midday. As we head into the afternoon hours, the atmosphere will grow increasingly unstable. A few stronger storms may develop and track across some of our north Alabama counties during the mid to late afternoon hours.
The Storm Prediction Center has portions of north-central Alabama in a Level 1 of 5 risk for severe storms for this afternoon and evening. The threat is very isolated in nature, but it's not zero. One or two storms may become severe with damaging wind gusts and hail. We also note that our in-house high-resolution Futurecast models shows these being individual cellular type storms. There is the potential that these may be supercells, and because of that, we also can't completely rule out a tornado. The Futurecast Updraft Helicity product shown above, when paired with the Future Radar product, shows which storms the model thinks are rotating. That doesn't mean that there will be a tornado there, but it shows that there is the potential for a rotating storm or two, and because of that, we can't rule out a tornado. Scattered storms will continue into the evening and overnight over northern Alabama as the front stalls across the area. Any risk of severe storms should end by mid evening as the atmosphere grows more stable.
Tuesday will be a day between storm systems. The frontal boundary will be stalled out across our area, but with sun breaks, even areas to the north of the front will climb well into the 70s. Most of the day Tuesday will be dry, but we can't rule out a stray shower completely in the afternoon. The Storm Prediction Center officially has a Level 1 risk for portions of north Alabama and Mississippi for Tuesday afternoon and overnight, but it is looking increasingly likely that any of that activity would stay off to the south of our area. Still, as we head deeper into the overnight Tuesday and into the early hours of Wednesday morning, we can't rule out a few showers or storms as the frontal boundary lifts back northward across the area as a warm front.
As we move into Wednesday, this is where the nature and magnitude of things change for our overall area. Already, the Storm Prediction Center has a large part of the coverage area in a Level 3 of 5 risk of severe storms, with the remainder in a Level 2 of 5 risk. It isn't all that often that a Level 3 risk is issued this far in advance. As we get closer and smaller-scale details are brought into light, these risk areas will get adjusted. Don't be surprised if more or the rest of the viewing area is upgraded to at least a Level 3 risk, and don't be surprised if the risk is eventually upgraded beyond Level 3. It is the smaller-scale details that we don't yet have a full handle on (but they are starting to come into focus now) that will ultimately determine the exact magnitude of this threat, but the overall setup is one that has produced significant large-scale severe weather many times in the past.
The main overall timeframe for our viewing area for this threat begins in the early to mid afternoon, possibly as early as 2:00pm. However, we can't rule out a strong storm or two even during the morning hours as the warm front lifts rapidly northward across our area. The cold front/dryline doesn't clear our area until after midnight, and this extended time from mid afternoon until then, the door will be open for severe weather across the viewing area. This is not one of those cases where we can give a short duration time window for one line of storms, and then the threat is over. This is a long-duration type threat where there may be multiple rounds of individual supercell thunderstorms.
The overall combination of atmospheric parameters supports any storm that develops being capable of producing all threat types: damaging straight-line winds of 60-70 mph, large hail that may range from quarter size in most warned storms to as large as golfball size in one or two of the storms. There will also be the threat of tornadoes. Now that we are getting the first glimpse at some of the smaller-scale details of this setup, we are getting increasing confidence in the tornado risk across the viewing area. The parameters in place support the potential for there to be several tornadoes across the overall general region, and a few of these may be the long-tracked and strong or possibly even violent variety. This is not an "average" or "low-end" severe weather threat. This is a potential high-impact severe weather event that is capable of significant damage. Those of you that have followed us for a while know that we don't like sounding alarms here at the Tennessee Valley Weather Channel. We do our best to avoid it unless the situation really calls for it. However, based on everything we see, we have to call it like it is. We don't want to scare you; that goes against who we are and our mission. But our job is to inform and prepare you. When we have a threat of this nature, because of the trauma from 4/27/2011, some people ask if it will be like that day. The immediate answer is no, we have no reason to believe that it will. However, it doesn't have to be like that day. Think of all the other big tornado events in our area over the years that weren't like April 27th, 2011 but still produced major tornadoes with high-end impacts. All it takes is one tornado impacting you personally, and it is your personal April 27th. However, this is one of those situations where there IS the potential for a few of the tornadoes to be large, long-tracked, and strong to possibly violent.
Your best defense on days like this is being aware and being prepared. If you're following us, you will be aware because we will update you frequently on the latest information as this unfolds. What you can do now is make sure you are prepared. Above are some general guidelines to use when formulating the plan for where you will shelter if a tornado warning is issued. The other important step is to make sure you have multiple reliable methods to receive warnings. We recommend at least two, not including outdoor warning sirens. Our FREE Tennessee Valley Weather App is one such source, and it's available for download in your appropriate app store. We also recommend a NOAA Weather Radio as the baseline for receiving warning alerts, especially if you are asleep... which may be the case since this threat will extend into the overnight hours.
We will have frequent updates the next few days with updated information as the details of this threat become more clear. Keep checking back for new information. Remember, if you're working with old weather information, you're working with bad information. Forecasts are updated as new data arrives and details become more clear. Forecast information has an expiration date, just like the milk in your fridge. We will be fully staffed in the Tennessee Valley Weather Center to provide live coverage as the event unfolds on Wednesday, including live non-stop coverage for any tornado warnings in our viewing area.