Northern California is bracing for another winter storm this week, which is set to bring heavy rain and snow and impact holiday travelers. Here's the timing and totals we're expecting.

We are tracking the return of the polar vortex next week as a wavy jet stream brings a blast of Arctic air to the Great Lakes.

A week-long, polar vortex-related Arctic outbreak rivaling any seen so far this winter is slated to bring frigid conditions to much of the U.S. east of the Rockies next week. Threat level: The Arctic air is likely to send temperatures plunging to at least 30 degrees below average for mid-February across the Midwest and Plains states,