The Storm Prediction Center has indicated a slight risk for severe weather in the Tennessee Valley Thursday, but there is a possibility that storms remain below severe limits -- if they develop at all.
In order to have thunderstorms, two ingredients must be present: atmospheric moisture and a lifting mechanism, like a cold front.
We are confident that the two ingredients will be available: Southerly winds will return to the Southeast Wednesday, allowing warm and humid air to flow into the Tennessee Valley, supplying the atmospheric moisture. This will allow the atmosphere to become unstable -- air parcels will have a tendency to rise and produce rain clouds.
By Thursday, a cold front advancing from the Great Plains into the Southeast will provide the lift necessary for the air parcels to rise rapidly into the atmosphere. This rapid rising motion provides a lot of the dynamics that drive the development of severe weather.
So what would throw a wrench into the development of severe storms Thursday? The clue is located over the Gulf Coast.
If a cluster of thunderstorms develops along the Gulf Wednesday night through Thursday afternoon, it will ingest a majority of the atmospheric moisture that would have been available for potential storm development in the Tennessee Valley. In other words, the Gulf storms would "rob" the Valley of the moisture, or "fuel" necessary for storms to fire up in northern Alabama and southern Tennessee. Rain will likely still develop, but the showers and storms would not have as much "punch" to them if the Gulf storm complex did not develop.
With that said, if the Gulf storm complex does not materialize late Wednesday through Thursday afternoon, then the likelihood of Tennessee Valley severe weather increases.
We will continue to monitor this situation as we go through the next few days.