From James Spann and the ABC 33/40 Weather Blog:
QUIET SO FAR: Despite a very unstable environment, so far severe storms are a no-show across Arkansas, West Tennessee, and the northern part of Mississippi and Alabama despite the current tornado watch in effect. Seems like a capping inversion (a “cap”) a few thousand feet off the ground is keeping air parcels from rising to the level of free convection, when storms would then go up.
There is basically nothing significant on radar as 8:45 p.m
SPC maintains an enhanced risk of severe storms for parts of North Alabama overnight, with a “slight risk” down to near Montgomery.
SPC maintains a tornado watch for parts of North Alabama and North Mississippi until 2:00 a.m.
*A digging upper trough should help to erode the cap, and thunderstorm initiation is still likely over the next few hours across the northern part of Alabama, Mississippi, and West Tennessee.
*If storms can develop, they have potential to become severe quickly. The main threat for Alabama will come from damaging straight line winds. An isolated tornado is possible.
*The main window for severe storms will come from around 10:00 p.m. until 3:00 a.m.
*Yes, there is a chance the cap holds and no convection forms. As we have discussed in recent days, handling thunderstorm events in a northwest flow aloft is always challenging.
*The bulk of the day tomorrow should be quiet with just a few scattered showers, but thunderstorms could fire up late in the day and tomorrow night, and those could be severe. SPC has most of Alabama in the standard “slight risk” (level 2/5) main threat of stronger storms will come from 4:00 p.m. until midnight.