Every highway out of this area is closed except for Interstate 5 going north from here. Which means the only place to go out of Seattle is Vancouver, Canada, except by plane, assuming flights aren't delayed or canceled due to things like storms or say a flooded or too-slick runway.
There's no way around, at least not without going through Canada.
Times like now make this feel like a lot less like a major urban area and a lot more like smack in the middle of literally nowhere. I can't imagine being completely unable to get from, for example, Boston to Providence or NYC by roads of any sort, but that is pretty much functionally analogous to what is happening here.
And it happened last winter too.