An unusual November snow event occurred on the evening of November 22 and continued into the early hours of the 23rd. The 22nd was mild and rainy for most of the day, but a strong cold front, backed by marine-modified Arctic air, passed through northwest Oregon late in the day.
In Corvallis, the front arrived in early evening, accompanied by strong west winds. Temperature and dewpoint quickly dropped. Snow began to fall shortly afterward, and continued overnight. Typical snow totals were 2-3 inches.
Below is a chart showing time series plots of temperature, dewpoint, wind gusts and sea level pressure at Corvallis Airport. Also shown is the view from my living room on the morning of the 23rd.