Chilly today, warming the rest of the week, severe storms possible Friday evening - Saturday AM
It is a much different early morning out there across the Tennessee Valley than it was on our Monday. After rain and severe storms yesterday morning, things are quiet now with high pressure settling in behind the big cold front. We're also below freezing over much of the area this morning, with temperatures already in the mid to upper 20s as of the 3:00 AM hour over southern middle Tennessee and lower 30s over northern Alabama. We still have a little bit more time to drop before we reach the daybreak hour.
As we head into the afternoon, clouds will once again start spreading northward into the area from a disturbance that will pass by us just to the south. High temperatures only look to get into the mid to maybe upper 40s. Going into the overnight, those clouds act like a bit of an insulating blanket, keeping temperatures from dropping quite as low. We look to bottom out somewhere between the mid 30s and lower 40s, depending on how quickly a clipper system moves through during the predawn hours to start clearing out clouds. There may be a light shower along that boundary. Futurecast still suggests a band of sprinkles or light showers, and we don't want to completely discount that. However, it looks like the majority of us probably stay dry. Clouds clear out behind that going into Wednesday, and temperatures warm into the 50s areawide.
That is the beginning of big weather changes that take us through the rest of the week. The high pressure that settles into the area behind the clipper on Wednesday shifts off to the east as the pattern remains progressive. That allows low-level winds to come out of the south going into Thursday, and the cold front that moved through Monday and stalled near the coast comes back north during the day on Thursday as a warm front. Temperatures get into the low or maybe even middle 60s by afternoon. Showers also start moving in Thursday afternoon into Thursday night. This is the northward push of more unstable and humid air into the area. By Friday morning, shower activity will begin shifting northward through and out of the area with time, and by late morning and midday, that warm front will be well north into the Ohio Valley, putting us into the warm sector of an approaching storm system for Friday night into Saturday. Temperatures look to climb well into the mid 70s Friday afternoon, with dewpoints in the mid to upper 60s, if not flirting with 70 degrees in a few spots. We can't rule out some locations possibly making a run at upper 70s during the afternoon, especially in northwest Alabama and northeast Mississippi.
As the storm system approaches late Friday into Friday night, strengthening wind fields will begin to get into place along with the humid and unstable air mass that will be over the area. Ingredients will become increasingly favorable over a large area for strong to severe storms, starting around midday back in Arkansas, north Louisiana, and southern Missouri... and then spreading east of the Mississippi River into the Ohio and Tennessee Valleys from late in the day or early evening, through the overnight, into Saturday morning. This will be an overnight threat for our area, although it may start a bit earlier than that. Often times, overnight timing helps to reduce the threat because of a lack of instability. However, the instability is one of the things that has never been in question with this setup when we've been looking at it over the past several days. Now that models are coming into line with one another, our confidence in a potential severe weather event of some magnitude over the area is increasing.
The general timing for our area runs from about mid evening Friday, although we will have to watch as early as the mid to late afternoon with some models hinting at a renegade storm or two, and that time window stretches all the way through the mid morning hours of Saturday. This will be a long time window in which there may be more than one round of strong to severe storms. This will not be an event where we are just timing out one individual line of storms with small 1-2 hour threat windows.
This is an areawide storm threat across the Tennessee Valley, with all of our viewing area included in the potential for strong to severe storms. We are still working out the details of the behavior of the storms... whether they will be in a line, individual cells, or both... and if in a line, whether there may be supercells embedded within that line. That will help determine the ultimate magnitude of the threat, and that's something we're still working on. However, it does look like an ordeal where all threat types (damaging straight-line winds, hail to at least quarter size, and tornadoes) will all be possible. As far as the tornado risk goes, it is too soon to say the exact magnitude of that risk and the "type" of tornadoes that may be possible. However, we do feel comfortable enough in saying that risk will be greater than what we had with the system back on Monday morning.
We will continue to fine tune the details of this threat over the coming days. Be sure that you stay in touch with updated weather information every day as we get closer. Take the time now, while the weather is quiet, to review your severe weather safety plans and make sure you have multiple reliable ways of hearing warnings. Remember to take into account that this will be an overnight threat, happening when most of you are sleeping, as you formulate your plans.
The system pushes the cold front through the area as we work later into Saturday, with the threat ending by the late morning to midday (as of the current timing). Temperatures drop the rest of the day behind that front, and we're back to near freezing by Sunday morning, with afternoon highs back in the 50s with clearing skies from Sunday going into early next week.