Looking at years that had a high NPS for Oct and Nov combined the picture is even more clear than with just a high October! Looking at the 8 highest such years on record with neutral or cold ENSO we have the following.
1948 - Coldest winter on record for SEA, second coldest Jan
1956 - 11th coldest winter on record for Puget Sound Lowlands since 1895, third coldest Jan for SEA
1961 - Significant Arctic blast in Jan, historic late blast in Feb / early Mar
1971 - 3rd snowiest winter on record for SEA, major snowstorm and blast in late Jan, 17th coldest winter for Puget Sound since 1895
1978 - 7th coldest winter on record for Puget Sound since 1895, prolonged cold
1985 - Coldest Nov on record for SEA, coldest Nov / Dec combo in recorded history
1990 - Coldest Dec on record for SEA
2013 - Major blasts Dec and Feb, major snows in Oregon and SW WA
I think I have really stumbled onto something here. Amazing correlation!