What are some of your favorite tier 3s along those pathways?
CA Yes to Bear Valley. Maybe Homewood, which I haven't skied yet. Mt. Baldy has great terrain quality when it has snow, which hasn't really been since 2010. My favorite "second line" area at Tahoe is Mt. Rose, but with 2 high speed lifts it;'s probably a Tier 2 by this thread. June Mt. is a 3 despite high speed lifts because it's such an afterthought these days.
OR/WA Is Mt. Baker a tier 3? Probably and if so clearly the winner of the PNW with its copious snow (most years) and very challenging terrain, though short vertical.
UT Sundance, Powder Mt. for the time being. Terrain not that interesting at other possibilities IMHO.
ID Definitely yes to Brundage. Out of the way is what makes a lot of these places attractive. It's one of the best places anywhere for non-competitive intermediate powder skiing in well spaced trees. Silver Mt. is a moderately interesting 3 despite an access gondola.
SWCO Durango is a Tier 2 (high speed lift, resort infrastructure). Isn't Wolf a 3 until it gets a high speed lift? Monarch, Sunlight, Powderhorn are moderately interesting 3's.
NM Apache is probably a 2 (gondola, resort town nearby in Ruidoso). Sante Fe is a moderately interesting 3. Pajarito is interesting by reputation though I haven't skied there. Other places have a reputation of being very flat. The one I've skied, Sandia, certainly is.
AZ Snowbowl is a 3 until it gets lift upgrades.
MT is the US hotbed of interesting 3's. Snowbowl and Discovery have some kick-ass terrain. Lost Trail and Lookout are great powder stashes. I haven't been to Turner, but it obviously qualifies. Bridger is a 3 by the OP definition.
But the undisputable best Tier 3 mountain in North America is Castle Mt. in Alberta. Maybe it's not tier 3 with 2,800 continuous vertical, but in terms of lifts, base infrastructure and skier visits it otherwise fits the definition perfectly.
Edited by Tony Crocker - 4/12/15 at 4:40pm