11.   In the wake of the front, seasonably cold Pacific air will spill into the upper Middle West.

12.   Meanwhile, arctic air will spill over the Rockies into Washington and Oregon, driven westward by a very strong high-pressure system over the Yukon.

13.   Meanwhile, cold Arctic air spilling southward will allow moderate to locally heavy snow to eventually develop as far south as the panhandles of Texas and Oklahoma.

14.   Mild air will spill eastward from the Rockies, causing cold air to gradually retreat from the Northern Plains and western Great Lakes States.

15.   On Monday, the frigid air will spill southward into British Columbia and northern Alberta as an intense low pressure system crosses the Canadian Rockies.

16.   Very warm and more humid air will spill into the Middle Atlantic and Northeastern states Friday.