This list really is amazing. Not one of those winters failed to deliver Arctic air to the NW. Many of them delivered big time. In that list of years you have the coldest November of the 20th century (1985), second coldest November (1955), coldest January (1950), two of the coldest Decembers (1983 and 1990), two other notably cold Januarys (1943 and 1957), Even the 21st century years delivered cold / snowy months.
Last Winter's N. American pattern fit Strong El Nino/-PDO almost perfectly. You could have used only that and gotten it near perfect. ENSO actually has a 30-40% correlation with the PDO, it's bigger effect is on the North Pacific High, which is off the west coast, vs the PNA which is more west-based Pacific events, and more associated with PDO patterns. The North Pacific Ocean circulation is not really aligned with equilateral ENSO SSTs, they are at different longitudes.. I would take a +PDO/La Nina any day. La Nina's are cold and dry. El Nino's are wet and warm. ENSO effects more of the eastern Pacific.
I realize that other things are bigger drivers in the grander scheme, but when the PDO is record breaking it bears some considering if nothing else, than because of how much of a predictive tool it's been the last few Winters. I know the CPC is using it for their Winter forecast this year.