Solid contender for greatest snowstorm in regional history between February 18-19, 1884.
After a two week cold spell, a major system moved in off the coast and moved north up through the region while dropping tons of wet snow in its wake.
In the Willamette Valley on the 18th, the Oregonian reported 11 inches at Junction City, 24 inches at Corvallis, 20 inches at Halsey, 16 inches at Albany, 12 inches at Salem, and 16 inches in McMinnville. In Portland, about a foot fell with this storm with the paper reporting snowfall rates of 1.5" per hour throughout much of the morning of the 19th. The snow was so wet in town that the paper reported roofs caving in. By the evening the wind switched to the south and the entirety of Western OR was in the 40s.
The storm continued to spread northward , dropping 12"+ at Olympia and a reported 18 inches fell in downtown Seattle between the 18th and 19th. Downtown Seattle looked like this on the 19th before warming into the 40s
It appears this initial storm cut off somewhere to the north of Seattle, with Langley, B.C. reporting an overrunning total of 7" on the 21st with what was likely a 2nd storm.
However, it is definitely one of the only individual events that I'm aware of to drop 10"+ essentially from Eugene to Everett. Certainly no 21st century precedent for it.