The Storm Prediction Center has posted a MODERATE RISK of severe storms for parts of the Midsouth on Tuesday.
This storm system is very potent, and the reason the risk is higher to the west of the Tennessee Valley is pretty simple: instability and shear will be more balanced near the Mississippi River Tuesday afternoon through Tuesday night than it will be as the system advances into North Alabama and Southern Middle Tennessee.
As this system moves northeast (rapidly) into the Tennessee Valley on Wednesday morning, our primary risk will be strong, straight line winds in excess of 60-70 MPH; however, given the nature of the system and the strength of the wind field in the lower atmosphere, there is at least some tornado threat between 2 AM and 10 AM Wednesday. (The graphic above only represents the storm risk through 6 AM Wednesday; the risk is SLIGHT for North Alabama and Southern Tennessee during the day Wednesday.)
This is a forecast for a threat of storms over a broad area; we cannot be specific about an individual town, community, or county because the thunderstorms happen on a different time and space scale than the bigger system producing them.
The storm system is like an 18-wheeler traveling down the interstate. It’s easy to pick out the path and time the system, but it’s a lot harder to know how the freight in the trailer will shift when that truck speeds up, slows down, or hits a pot hole. In other words, the small-scale things that enhance or interfere with individual thunderstorm development are tracked and forecast on a scale of minute to an hour or two. That’s why you should be ready in case a warning is issued for your community. Have a NOAA weather radio handy tomorrow night into Wednesday morning, and there are a number of other ways to stay informed as well.
We’ll be here to keep you updated!