We started talking about a threat of strong and severe storms about a week ago, and we are still on track to deal with the not-so-pretty side of spring weather later this week. Up front, there is no skill in forecasting individual storm behavior more than an hour or two in advance; that means no matter how much I “would if I could,” I can’t tell you specifically if your house, school, workplace, etc. is in any greater or lesser danger than anyone else.
The Storm Prediction Center doesn’t think much of this event for the Tennessee Valley right now; they do, however, see a much higher threat to our west and northwest on Wednesday. This is the Day Three Outlook and the probability of severe weather.
Here’s a snippet from the discussion:
...STRENGTHENING LOW/DEEP-LAYER SHEAR SHOULD PROVE FAVORABLE FOR SCATTERED DAMAGING WINDS...A FEW TORNADOES...AND ISOLATED LARGE HAIL. AS FLOW BECOMES INCREASINGLY PARALLEL TO THE COLD FRONT...AN EXTENSIVE QLCS MAY ULTIMATELY FORM PRIOR TO THE FRONT REACHING THE MS VALLEY.
There are several words in that paragraph that will grab your attention. “Damaging winds,” “tornadoes,” and “hail” are the obvious ones, but there is one that you might have just skipped over unless you’re well-versed in reading government-issued forecasts – “QLCS.”
A QLCS is a quasi-linear convective system. That’s basically a line of intense thunderstorms that often breaks up into smaller segments that bow out or break free and go into rotation. The tornadoes and 100 MPH+ straight-line winds on March 18th were caused by a QLCS that hit a pocket of higher instability in Colbert County as well as Marshall, DeKalb, Cullman, Blount, and Etowah Counties.
Tornadoes that come from things can be hard to detect on radar (see “Why RADAR Can’t Catch Every Tornado” to understand that statement a little better). Sometimes they can be caught in advance; sometimes they cannot. That means you have to be extra-vigilant when storm systems like this approach.
So, here on Monday afternoon looking toward Thursday, our general ideas about this situation on Thursday look like this:
(1) There is a lot of uncertainty around exactly how strong these storms will be here. A lot of that has to do with timing. If they come in early in the day when temperatures are cool, they’re less likely to be extremely strong.
(2) We expect a threat of strong or severe storms with heavy rain, hail, strong winds (over 50 MPH), and a low-end threat of tornadoes between 5 AM and 3 PM. Let’s be clear here, it’s not going to storm that entire time. The most likely scenario is that they come in early and are gone by Noon; however, since we have uncertainty in the timing, there is a chance they could come in around mid-morning and last through early afternoon. Here’s the latest Futurecast looking out toward that time; it shows an intense line of storms in The Shoals by 6 AM, in Cullman, Decatur, Fayetteville and Huntsville by 9 AM, and near Sand and Lookout Mountains in Jackson, DeKalb, Marshall, Cherokee and Etowah Counties between 10 and Noon:
*Times will vary; this is only model guidance – do not plan or alter outdoor activities based on this single piece of the puzzle.
The Bottom Line: Don’t get too worried just yet; if the ingredients come together for this, there could be some rough weather similar to what we saw on March 18th. It may not affect the exact same places, but the end result could be similar for a few communities in the Tennessee Valley. All you need to do now is prepare. Make sure you have a NOAA Weather radio and a way to stay connected IF your community is the one affected. WHNT News 19 offers several FREE apps and recommends a few that you have an option to purchase (we make no money from the sale; we just recommend it), and we have multiple ways to stay in touch:
As always, it’s better to be prepared and have the knowledge something could happen than to be unprepared and unaware of a threat. We’ll keep you posted this week!