Thanksgiving travelers planning to drive on Northwest freeways Sunday night may want to consider returning earlier.

The National Weather Service in Portland says "weather is expected to rapidly deteriorate across the Pacific Northwest."  Forecasters predict heavy snow on Cascades highway passes in Oregon and Washington Sunday evening, with accumulating snow also possible in the Oregon Coast Range.

Forecasters expect very cold arctic air to follow, though details are uncertain. The weather service says there could be rain and snow at low elevations during the Monday evening commute in Portland, followed by even colder air that would likely bring the lowest temperatures since November 2010.