|Both images from RAP Weather|
Until tomorrow morning. Significant pressure differences to start with will provide some ignition for these storms. The tornado risk indicates some tornadoes should occur, as well as a significant hail event. A strong lifting mechanism will be needed.
The reason tornadoes may be likely is due to a high Bulk Shear- Effective value. If the values are between 25-40 knots, that is when supercell probabilities begin to start. In recent times tonight, even before the supposed outbreak, the Bulk Shear was up to 55 knots in some places of the severe weather risk area. By the way, that risk area is in Southeast Oklahoma into South Arkansas. Below is an image of that risk area.
As stated below, temperature differences over the South Arkansas area could make the scene intense. We will definitely have to watch this unfold as it may happen into the early morning hours.
Back in the Rockies, low pressure will create for a mix of snow and icy conditions across the mountainous region. Avalanche risks may be on the rise, so be careful if you ski in those areas.
A strong low pressure off the coast of Washington will create yet another messy day tomorrow. It will be carrying an occluded front. That said, the atmosphere is expected to be somewhat capped, limiting some thunderstorms. However, with the ocean moisture, this will be hard to tell.
Temperatures will be cool to cold across the northern tier of the US.