Just a heads up...Looks like I-5 to Michigan is the way to go for those coming from the North.
http://www.wsdot.wa.gov/News/2011/06/060711_99.htm
5 a.m. Saturday, June 11: All SR 99 lanes between the West Seattle Bridge and Battery Street Tunnel will close.
10 a.m. Saturday, June 11: Northbound SR 99 between S. Royal Brougham Way and the Battery Street Tunnel will reopen.
5 a.m. Monday, June 13: The remaining sections of SR 99 between the West Seattle Bridge and Battery Street Tunnel will reopen.