Arctic Air will move out of western Canada and into the United States during the middle portion of the upcoming work week.
The long-range forecast models moderate the arctic air a bit but keep it hanging around through at least December 15th.
The next image (courtesy TropicalTidbits.com) shows the temperature “departure from average”. You can clearly see the bitterly cold air sliding into the upper midwest, Rockies (on or around December 7th) and then bleeding eastward into the Mid-Atlantic and South (December 10th).
What was an unending summer and slow start to Fall is quickly going to morph into true Winter conditions with highs well below normal for even “January” standards.