The southern part of the region is really, really due a legit Arctic airmass. Pretty sure 1/3/2017 was the last time an upper-level Arctic airmass made it to the Oregon/California border even on the eastside. Even then, it didn't make it far past Alturas. December 2013 was the last subzero low at Reno and the last subfreezing high at Roseburg, longest stretch on record without one in both cases.
If there's anything we're also overdue for, it's probably a legit fake cold spell like January 2013 or December 2005.