Unsettled weather pattern continues ahead. Storms more widespread today, a bit more spotty Saturday/Monday, Still watching Sunday night for severe threat!

We’re mostly quiet as of the time I’m typing up this discussion early on this Friday morning. We’ve had a few spotty showers develop on radar back over northeast Mississippi. I’ll be showing you a “Futurecast” in a moment that has storms waiting until later this morning before developing. I can’t completely guarantee things will hold off that late with us already seeing a few showers just west of our area NOW, but I do think the more widespread and heavy action does wait until the late morning or midday and after. Otherwise, clusters of storms are located off to our west over the Arklatex, and that disturbance will act our weather later today and tonight. Temperatures across the Tennessee Valley are seasonably mild this morning with most all of us in the mid to upper 60s.

The early morning update from the NWS Storm Prediction Center maintains a Level 2 of 5 risk of severe weather for the majority of our viewing area for today and tonight, even though the orientation of it has shifted around very slightly. It now runs along and west of a line from Hohenwald TN to Pulaski TN to Athens AL to Hartselle AL and westward through the area. East of there, there’s still a Level 1 risk of severe storms for the remainder of southern middle Tennessee and north Alabama. Threats with this have not changed. It’s a low-end risk of a few storms with gusty straight-line winds of 40-65 mph and hail that may try to be as big as quarter size, along the non-severe-warning type threats of lightning, heavy rainfall, and maybe some isolated flooding. While the tornado threat is never completely zero with a severe thunderstorm, it continues to be VERY LOW for today and tonight.

Here’s our best attempt at being able to show a “Futurecast” type of visual aid for breaking down the general timing and evolution of storms for today and tonight. And before we get into the breakdown of this, look… Linda, listen…. These computer models, all of them, have been absolutely atrocious all week with trying to handle the specific timing and evolution of these thunderstorm clusters. That’s because once we start getting into the late spring and early summer, the jet stream disturbances are usually less intense, and that means that these thunderstorm clusters are more controlled by what the storms in the 24 hours before them have done and then by their own inner mechanics… NEITHER of which are ever handled that well to exact detail by models, because it’s simply beyond the current reach of the science. Maybe one day we’ll get there, but as chaotic and fluid as the atmosphere is, that may be beyond our lifetimes. Having said that, just because I can’t show you raw model data that has the exact placement of an individual thunderstorm at the exact minute over the exact town 24 hours in advance 100% correctly, doesn’t mean we don’t have confidence in the overall idea of the forecast. These models and these “Futurecasts” are just raw data and TOOLS used to make the forecast, and they are not all we use. It’s the actual PEOPLE on this weather team, with knowledge and experience, that make the forecast itself.

With all that said, here’s the general idea of how this breaks down for today and tonight…. At some point during the morning to midday, showers and thunderstorms will start to become more numerous with time across the area as we get a little daytime heating and the atmosphere grows more unstable. These storms will continue to develop and mature into the afternoon and evening. During this time, a few of them may be strong to severe with those main threats of gusty winds and hail that we talked about earlier. Depending on how they try to cluster together or not, there’s the potential for them to be widespread enough to trigger a severe thunderstorm watch at some point today, but that’s not certain. Even if a watch is not issued, there may be a few severe thunderstorm warnings. This potential continues on into the mid evening or so. As we get later into the overnight and into early Saturday morning, the HRRR (and other models to an extent) bring in another complex of storms from the northwest. While we can’t rule out gusty winds or small hail with these, they will have a lower potential for being severe because of the loss of daytime heating and the atmosphere getting worked over from storms earlier in the day. I will caution to not take the HRRR images above for this late overnight period at absolute face value especially, because this part of the timeline is more uncertain with how widespread the storm coverage will be. While other models do show additional storms after midnight like this, they’re not quite as widespread and organized with a cluster of them. It’s just that this HRRR model is the closest overall to reality with the next 48 hours that I can use as a visual aid to give a general idea of the timeline and storm evolution. That doesn’t mean that each exact image is going to be exactly correct.

Before we get into detailing Saturday’s storm threat, we will say up front that things have trended a little bit better for outdoor plans for the Memorial Day weekend. Especially if this HRRR model is closer to correct, there may be little in the way of storm activity Saturday, Saturday night, or even in the daytime hours of Sunday. We’re NOT ready to remove rain chances even though some models are a lot drier during this period, but we HAVE lowered them some. Still, we can’t just assume it’s going to be dry during this period with a moist and unstable air mass in place and a stalled frontal boundary nearby. Still have indoor backup plans for Saturday, Sunday, and Monday and pay attention to the weather so you know when and if a storm is coming up so you can run inside, but it is looking a little more manageable for daytime outdoor plans. We’re still watching Sunday night for a more organized severe storm risk, but that has trended more solidly toward the after dark hours. We’ll talk about that in more detail in a moment.

The early morning update from the NWS Storm Prediction Center has actually shifted Saturday’s Level 1 of 5 risk south of our region and removed our viewing area from it. This is still VERY QUESTIONABLE though and is built mainly around this trend toward more widespread storms Saturday morning that may work over the atmosphere and temporarily push Saturday’s lift and instability to our south. That’s not a guarantee though…

The latest HRRR model here outlines how this might happen. IF the predawn storms Saturday morning left over from late Friday night are more widespread, this would work over the atmosphere during the morning to midday hours of Saturday, and then there would be sinking motion in the atmosphere behind this wave that would likely put a cap on the atmosphere for Saturday afternoon and Saturday night. We caution though, that this is NOT GUARANTEED to be the case. IF the storms early Saturday morning are NOT this widespread, they would influence the environment for later in the day less, and there would be the chance for scattered strong storms Saturday from midday or afternoon into the evening. There are a few models that show this happening. We may not have a good handle on how that plays out until we get to tonight and we see how these overnight storms tonight are going to behave. The best course of action for Saturday is to not cancel your plans, but still have those alternate indoor plans ready just in case… but some of the data for Saturday IS trending toward us possibly being less stormy. We just can’t guarantee it yet!

Sunday is when we’re still more concerned about an organized severe storm threat, but it has trended more toward the after dark and overnight hours for our local area. The early morning update from the NWS Storm Prediction Center maintains a Level 2 of 5 risk of severe storms across our entire viewing area. However, they have not only shifted the elevated Level 3 risk off to north of our coverage area, but they’ve shifted it north out of Tennessee altogether! This is because the upper-level dynamics have trended a bit flatter, disjointed, and farther to the north. While we can’t rule out a stray shower or storm during the daytime, this will not only keep most of the daytime hours Sunday dry, but it will keep that higher supercell tornado threat threat solidly north of our area as of how it looks now. We’ll still watch to make sure it doesn’t trend in the other direction, but trends in the data for the past 12-24 hours have been shifting that higher supercell tornado threat solidly north of our coverage area of southern Tennessee, north Alabama, and northeast Mississippi. Now, it’s even trending north of even northern Tennessee, but we’ll see.

What we DO expect to come through the area is an organizing and solidifying line or cluster of thunderstorms overnight Sunday night into predawn early Monday morning. Because this will be a line of storms, while there will still be the potential for a few tornadoes involved, we’re talking more of the spin-up variety. A tornado is a tornado though; so, don’t think that it’s not something you have to take seriously, just because we’re not talking about long-track supercell tornadoes. It doesn’t matter. But this does mean we’re NOT talking about a higher-end tornado threat at this point. We’ll watch to make sure that doesn’t change, but that type of tornado threat has trended off to the north of our area. What’s most likely with the line of storms is the potential for pockets of damaging straight-line winds of 50-70 mph along the line. Y’all know how this works. NOT EVERYBODY gets that type of wind from the line, but some embedded areas in there will. We also think that there may be some hail to quarter, half dollar, or even ping pong ball size with a few of the storms. In addition, frequent lightning and maybe some localized flash flooding will be concerns as well.

It’s still too far out for the exact timing of this line. We’ll start honing in on those details by Saturday. However, it does look to be more likely after 9-10pm Sunday night into the predawn hours of early Monday morning. Some good news is that things are trending toward these storms possibly pushing the more unstable air mass south of us for Monday and reducing what was still a fairly widespread shower/storm chance for Monday to maybe just a few lingering heat-of-the-day spotty showers and thundershowers. We’ve reduced Monday rain chances down to 30% because of that. We’ll start getting increasing confidence in that as we get greater detail in how the Sunday night storms will behave.

Behind that system, we look to get into a drier and slightly cooler weather pattern for next week that may possibly last as long as into next weekend. Daytime highs from Tuesday onward look to step down into the upper 70s to lower 80s, with overnight lows being allowed to get down into the upper 50s with drier air moving into the area. After the already downward trending rain chances for Monday, rain chances go away beginning Tuesday, and we MIGHT be able to keep them out of the forecast locally for the rest of next week! We’ll see how that goes as we move forward in time…