I think the FAA puts out an advisory and the planes just fly around it. It won't affect SeaTac or Portland much unless the ash cloud moves over those cities, which it hasn't (moved to the east). another news link is http://www.katu.com I'm going to Portland on Saturday--it would be something if it was still spouting off!
Isnt this what happened in the 80's as well. There was a lot of mendia and expectation....people got sick of it and the hype died down....and then BOOM!