Since you apparently have an early morning flight the next morning, I suggest that you buy a one-way full flex (fully refundable) ticket on www.alaskair.com YVR-SEA before things possibly get worse as an insurance policy.

The roads and rails are not yet closed, but the Skagit River in flood normally closes both between Bellingham and Seattle. Additionally, television and web-sites have shown the flooding in Bellingham which should get worse as the storm dumps more rain.

Your choice.