Unless you like rain, I'd skip Seattle if I were you(this coming from a Seattleite). Summer months are best to visit instead(sunsets occur around 9:30pm vs 4pm in winter). However, if you enjoy skiing/snowboarding and still want to visit Pacific Northwest, then skip Seattle, travel up north to Vancouver, BC for great sushi and 2 hrs further north to Whistler - the best snow resort in North America. It's a great melting pot. You literally see people from all over the world.
On this leg of your trip though, it'd be a hassle to drive all the way up here. If you are into snow sport, I'd hit Lake Tahoe instead.
Enjoy.