I used to live near PUW (72mi away) which has similar issues with fog, wind, ice, and other winter wx problems AND it doesn't even have an ILS.

I still booked flights out of PUW even though it was more prone to delays and cancellations due to the shorter drive. Alaska was generally pretty good at re-accommodating me via GEG if needed. Delays happened, but they didn't happen enough to make me want to drive an extra 90 minutes.

My biggest issue would be the timing of the 2x daily flights out of ALW. Depending on where you are flying, you could have some LONG layovers in SEA.