We are talking about the coldest temperatures in 3-5 years for many locations. A hard freeze capable of damaging plants and freezing some exposed pipes.
And then there will be snow tomorrow over Oregon, the southern Cascades, southwest Washington, and much of eastern Washington.
Let's "warm up" by starting with the low temperatures on Tuesday (below). Upper 20s and 30s over western Washington, teens in the mountains, and single digits of NE Washington. A few negative temperatures in some cold pockets, generally in valleys. Before long you will be thinking of these temperatures as subtropical.
One way to show you the changes are with forecast maps of sea level pressure (solid lines) and 925 hPa (around 2500 ft) temperatures (colors). Blues are very cold and purples you don't want to know about.
Currently, cold air is found east of the Cascade crest with cool air over NW Washington.
Weather.com, which uses sophisticated statistics on top of combining a number of major weather models, projects a high of 33 and a low of 21 on Friday.
And did a say something about snow? Yes, I did! A low pressure center will move across southern Oregon tomorrow, producing a shield of snow that will move across Oregon and SE Washington.
Here is the 24 h snow total ending 4 AM Thursday. Eastern Oregon really gets it, with the eastern slopes of the Oregon Cascades BURIED with several feet of snow. Folks around Mt. Batchelor will be smiling. Portland may get a small piece of this, as might Yakima and the Tri-Cities.