I was in Spokane about 14 years, but I also spent 7yrs outside Yakima just before Chinook pass (we got snow like you do) and teen age years in Tri Cities. Moved to Wisconsin 4 years ago for my job. In the SE part of the state we get insane cold, but not usually this much snow stacked up at once.It looks like we have almost as much as you! Not sure what part of Washington you lived in, I’m high up in the mountains outside the Wenatchee Valley... so we have about 3 feet in most open areas! But I’ve dug a good path out to some big pine trees where the ground stayed pretty protected. Our coop is 8x10 and I’m constantly kicking myself for not making it bigger
I think your setup will be fine! Especially if they’ve been doing well so far and their combs and wattles look healthy!
I put Vaseline on their combs. My barred Rocks and Sexlinks molted over the winter, so I also add electrolytes to their water and some extra protein. They are so spoiled lol