I live in north central Washington, across the Cascades from Seattle, though I was born and raised on the west side of Washington state.
You are correct ... snow in Seattle is rare, and when it happens, no one is prepared for it, no one knows how to drive in it ... and, trust me!
Even people who KNOW snow have never driven in that awful white stuff on the west side of Washington state and NW Oregon.
The snow is complicated by the fact that it is very wet, and very heavy ... not like most places receive snow, which is usually dry.