It’s rare that we have a warm stretch like we’ve had this December without any severe weather, but so far this winter we’ve been able to dodge any significant severe weather. That trend may not last through this week, though, as we’ve got a couple of rounds of storms that could be strong or severe this week.
Round 1: Wednesday
A weak cold front will approach the area from the northwest Wednesday, triggering some showers and storms. In the upper levels of the atmosphere, things aren’t going to look like a classic December severe weather event, but there’s just enough upper-level muscle to kick off some stronger storms Wednesday starting in the afternoon and continuing through the overnight hours.
Based on what the wind shear looks like Wednesday, we expect storms to develop in clusters and lines. Within these lines and clusters, the primary threats will be damaging winds, heavy rain, frequent lightning, and hail around the size of a penny or quarter. We’ll be sure to monitor for any storms that make more of an “S” shape, which would indicate a higher severe weather threat.
While tornadoes aren’t as likely as damaging winds or hail given the amount of wind shear we expect to be in place, we can’t totally rule tornadoes out, so it’s best to be prepared just in case, and don’t under-estimate the power of straight-line winds.
Round 2: Weekend
A second round of severe weather will be possible across the Southeast U.S. this weekend, and this second system looks to be a bit more potent. A strong upper-level trough will push into the Southern U.S. by the end of the week, with a strong surface low and associated cold front moving through the Southeast out ahead of the trough. Severe weather looks likely with this setup where the best mixture of wind shear, upper air lift, and unstable air meet. Models are still struggling on exactly how all that comes together though, and exactly how storms will time out across the Tennessee Valley.
A warm front will surge north Friday night into Saturday bringing showers to North Alabama, before Saturday evening a cold front approaches North Alabama and Southern-Middle Tennesee and slows down or stalls over the area, leading to a lot of heavy rain and potentially strong storms until the system finally swings east Sunday morning bringing very cold air and lingering rain through the day Sunday. Rainfall totals could approach 5″ this week, so some flooding will also be possible, especially this weekend.
This forecast could change quite a bit for the New Year’s Weekend, so be sure to check back often for updates.