There have been strong thunderstorms throughout the Plains, especially the northern Plains, where even at this late hour, there are severe thunderstorm watches from Wisconsin to Wyoming, including one around Sioux City Iowa that was recently issued.
This is the calling call of advancing warm air, these late night areas of convection. Storms can be strong, and will feed off of each other overnight, but will dissipate tomorrow morning.
Then, the next round will step in almost immediately. A more well organized area of low pressure will slide into the Plains tomorrow, and will generate helicity and updrafts within a juicy environment. The SPC has a much more perilous forecast for tomorrow. Check out the area that is hatched on this forecast map.
Storms will continue through the night, but the bigger threat will come tomorrow in the Plains. Expect some good video of some photogenic activity as it rolls through chase country.