Tunnel-style may be best for left coast snow (I include n-Calif with the PNW due to its propensity for heavy, wet snow--both in the southern Cascades and northern Sierra). An example would be the Early Winters Omnipotent, which Bill Nicolai specifically designed to fend off the heavy Cascade snow. It was highly regarded by NW climbers. I went with the single-wall EW Winterlite as a lighter, less "bomber" option after having a really bad winter experience with an a-frame "mountain" tent with separate fly. To this day the Winterlite is probably my best winter tent.
Regardless of design, you will still have to get up and dig out periodically. Here's where an igloo or snow cave can be superior (if a heck of a lot more work). You just have to keep your airflow open.
Originally Posted By Pika
IME there are really no tents that work really well in the wet snowfalls of the PNW. There are just tents that work less badly than others.
Well truly bombproof tents like the full weight biblers (bibler bombshelter, eldorado, etc. come close - you do still have to keep them dug out to some extent of course. You'll have a lot easier time with something like that than you will something like a shangri la in that kind of weather. Of course the tent is a heck of a lot heavier but hey - that's winter camping!
Would I carry such a thing the rest of the year or somewhere I don't expect to need it? heck no.
My Bibler Eldorado weighs in at 68 oz and is true winter expedition tent BUT it can flap in high winds, and a 3-4 pole dome tent makes a quieter storm tent. If you consider the Roman arch which carries the load down is parabolic sides and look at a dome, I think you can see that a dome can have a great snow load on it and the load actually doesn't crush the tent.
I have never shoveled out a tent at night. I refuse and sometimes I have to push up through a lot of snow in the morning to get out. The worse snow I ever camped in dropped about 30" of wet snow on us and it did try to crush the sides of my Eldorado in. Still I didn't shovel, still inside my sleeping bag, I put my back against one wall and my feet on the other wall and pushed the snow away about three times. This packed a layer of snow just outside the tent so it was kinda like having the tent pitched inside a snow cave. It was really quiet after it was buried.
The Moss Superfly4 pyramid tent that I have for sale was pitched between my buddies tent and mine as we were using it as a cook tent in the great storm. I heard the wood center pole snap in the night. If we had been in it, instead my buddy would have shoveled around it and we could have pushed the sides out. This pyramid has two large screened windows and an interior snow flap to put gear or snow on to seal the bottom down, so its a true all season tent. The trouble with a center poled tent in deep snow is that the snow builds up on the lower edges and if not removed it will either rip or snap the center pole. Jim
These are my own opinions based on wisdom earned through many wrong decisions. Your mileage may vary.