The set-up for severe weather and tornadoes this evening is typical for late-fall or even winter scenarios.
Over the past 24 hours, the amount of humidity in the air over Missouri had increased dramatically, aided by very strong southerly winds through a deep layer of the lower atmosphere. This has destabilized the air over the region. This type of set-up does not require afternoon heating to maintain itself.
In addition, the wind field is very favorable for maintaining severe thunderstorms. In particular, the lower level winds are showing good turning and increase of speed with height. This suggests that a few storms will accuire rotation this evening and some isolated tornadoes are possible.
A tornado watch is in effect for this evening. Storms have reached severe levels near the Joplin area at 5:30 p.m.
Keep an eye to the sky!