If you have to drive to Seattle next week, take I-5 instead. But still be prepared for winter driving conditions esp along the OR-CA border. Be sure to carry snow chains (and know how to put them on before hitting the road), extra clothes and food, emergency kit, flash light, etc. Also be prepared for highly windy and stormy condition in the Columbia River wind tunnel (after crossing the Columbia River bridge into southern WA).
Have a safe trip!