The 18th-19th is another very active time historically for snowstorms around here. Just wouldn't ever know it from looking at recent decades.
The 2012 storm is the lone exception of course. 6-12" fell from Seattle to Olympia with 12-18" falling around Chehalis/Centralia and in the gorge. A major ice event also occurred, with up to 3/4" ice accumulation in parts of the South Sound.
A forgotten storm on January 18-19, 1960 buried the region from Salem to Centralia with 6-12", at the tail end of a very solid cold period without a ton of upper level support.
A solid snow event for the Portland and Seattle regions on the 19th in 1957 as a major arctic airmass began to strongly seep in.
In 1950, after the epic Friday the 13th blizzard and subsequent cold snap, a major pattern shift began on the 18th as the southern jet roared in and brought the warmest air of that month. After a quick burst of snow and sleet on the 18th, a switch to rain and freezing rain occurred.
Over NW OR and SW WA, an atmospheric river would stall overhead while the low level offshore flow maintained itself, resulting in the most significant ice storm in PNW history. PDX would measure 1.98" of freezing rain accumulation on the 19th alone, with another 3/4" between the 18th and 20th. Massive amounts of damage occurred and many areas around Portland were without power for up to 10 days following this storm.
Heavy snowfalls up and down the I-5 corridor in 1935 amidst one of the more intense low level arctic blasts of the 20th century. That pattern probably deserves its own passage.
Another forgotten heavy snowstorm dropped 6-10" around the Portland area on the 18th-19th in 1933.
A blizzard and sleetstorm hit the entire region south of Olympia on the 18th and 19th in 1930, the 2nd significant storm in a week. Most of the region between Albany and Centralia had over a foot on the ground by the 19th, with subzero cold following.
A major arctic front crossed the region on the 19th in 1927. A rain to snow event occurred around the Portland area with 4-7" falling at the onset of a big time upper level blast. No measurable snow fell south of Corvallis or north of Toledo (shades of 1/10/2017).
That mid to late January timeframe from 1927 to 1937 was just unreal around Portland. In 1937 a backdoor arctic front hit on the 19th, in 1929 there was a modified arctic front on the 19th with a widespread light snowfall associated with it, and more modified arctic airmasses and sizable snow events occurred in 1928 and 1932 during this week. In other words, out of 11 years there only three (1931, 1934, 1936) which lacked significant cold/snow in this January 15-20 window. Over a 70% clip ain't bad for the heart of winter...