Continue west on 20 and you'll be going over one of the most beautiful roads in America, in my humble opinion. The North Cascades Highway has awesome views. Make sure you stop at the rest stop at the top of the pass. There are short trails with stunning views there. This highway closes early due to snow and is typically only open about 3-4 months of the year. It should be open through September but it wouldn't hurt to check when you get to Wenatchee so, if it's already closed, you can take the Stevens Pass route I mentioned a few paragraphs above.