Many numbers on that site are reasonable, and some are so close to what I have that I wonder if my site is the source. There are a few round numbers that are probably "brochure quotes." The ones that aren't reasonable or otherwise worthy of comment:
Jackson Hole 500: The new since 1998 Bridger gondola site is probably over 400, but it's cherry-picking. The long term mid-mountain average of 369 is the one to use, particularly since Jackson has considerably more terrain below that elevation than above it.
Nagano Japan 433: The Nagano Valley is well inland from the west coast and would not get nearly that much snow. The Nagano Olympic events were held in the Hakuba Valley to the west. The main area Happo One there probably gets aound 350 and the small Hakuba Cortina area to the north and closest to the coast in that area is probably over 400.
Banff Canada 400: This is probably the most overstated number I've seen anywhere, and in fairness I've never before heard of any of the resorts there claiming that much. The real numbers, all mid-mountain, are Sunshine 254, Louise 166 and Norquay 107.
Big Sky 400: Long term mid-mountain 261. We've

several times before.
Powder Mt. 400: It's nice to see them not claim 500, which is not reasonable in any way. Based on relationship with Snowbasin the real number is probably in the 350-375 range.
Chamonix France 377: I wouldn't completely rule this out from, say the top of Grands Montets, though even there I suspect it's very unlikely. The highest official number I've seen from the Alps is 346 at mid-mountain Andermatt, though secondhand a reliable source claims 400 for Zurs and Warth-Schrocken in Austria. And by the way the 346 at Andermatt is Nov-Apr: for the entire year it's 425. Chamonix does not have the word-of-mouth powder reputation that Andermatt, Zurs and Warth-Schrocken do,
Canyons 355 and Park City 350: Jupiter Bowl averages 366. Park City Summit House averages 291. I would be surprised if anywhere at the Canyons gets any more than Summit House.
Valle Nevado 311 and Portillo 295:
Portillo's long term average is 254. I think Patrick or anyone else who has visited both areas on the same trip will agree that Valle Nevado gets less snow than Portillo. Comparing a handful of seasons, I'd say Valle Nevado is under 200.
The Heavenly and Squaw quotes are accurate for upper locations.