I'm a native of the Seattle area, having lived there for nearly 2 decades (I grew up and went to college there).
The biggest event that goes on in Seattle that weekend is the Macy's Holiday parade (the morning after Thanksgiving) in downtown Seattle. It's nowhere nearly as big as the one in NYC, of course. Also, there is the lighting of the tree in Westlake Park later that evening.
Sales tax is very high in Seattle--9.5% (10% in restaurants/bars). It's one of the high sales taxes in the country.
I've only been to the downtown Seattle Anthropologie store once, but I've been to the Seattle Barneys several times. I'm not aware of any Black Friday specials for either store, however.