I think one reason Mammoth leads the late season is their snow condition... often mid-winter up top and salted corn toward main lodge and stump alley... resulting in great skiing top to bottom well into May.
It may be my "home area," but I've been around quite a bit and the above is definitely true. Memorial Day is consistently worthwhile except in the leanest years like 2007 and 2012.
Is Mammoth the best late season skiing?
What about Bachelor or Hood or Baker?
Timberline has very confined terrain vs. Mammoth or Bachelor. The Washington State areas have lower altitude and a marine climate which produces fewer overnight freezes and much less frequent corn. I'm somewhat curious how Blackcomb in May stacks up. Relative to its latitude Blackcomb's altitude is more like Mammoth/Bachelor, but I suspect it's more like Washington in terms of the marine climate.
I think Bachelor is the only place that compares to Mammoth for consistent spring skiing. The natural corn skiing from its 360 degree Summit cone is impressive. Part of what makes it so good up there is very low skier density, leaving the snow smooth and not chewed up by too much traffic. Unfortunately the lack of business is what prompted Powdr Corp to severely curtail Bachelor's spring season vs. Mammoth. Thankfully this year they have taken the very positive step of keeping Northwest open for the 360 degree Summit skiing until first weekend of May vs. shutting it down in mid-April.
Bachelor still cuts the closing time back to 1 or 2PM in April, 2-3 weeks earlier than necessary IMHO. Mammoth generally adjusts the operating hours each spring depending upon how the snow surfaces are holding up.
Bachelor has a firm closing of Memorial Day (the first few years of Powdr Corp it was a week earlier) for the public regardless of snowpack. The last 2 years they reopened for one weekend in late June/early July. Mammoth runs continuously until snow melts out of the Main Lodge area, with July 4 now being the last possible closing date.
In terms of natural snowpack Mammoth has enough to make July 4 in about 30% of seasons. Bachelor could probably do it at least 70%. With a big snowpack in March/April, Mammoth brings in race camps to pay the bills in June. Powdr Corp did not do that at Bachelor until last year, and while the racers were there, the area was not open to the public. Race camps and the public coexist just fine at Mammoth despite Bachelor having more open ski acreage available in May/June.
I have ripped Powdr Corp vociferously for curtailing the best spring skiing in North America at Bachelor. That said, they deserve credit for taking a key step this season in keeping Northwest open longer. I would actually recommend destination visits from afar while the 360 degree skiing is open. It's been that good for most of my April and later skiing there.
One aspect where Mammoth is still #1 is for steep terrain in the late season. Bachelor doesn't have that much and A-Basin now shuts Pali down in early or mid May. In big years Snowbird has plenty, but eventually it can be difficult to ski to the tram base.
Mammoth is definitely #1 here. Bachelor was comparable in 1990 but I doubt it now. Last year they salted for the racers but not for the public opening at the end of June. A-Basin and Snowbird do not salt. For intermediates salting is key to keeping groomers nice in May/June for 2-3 hours rather than about half an hour.
I don't know about Mammoth late season NYC, is about the same length drive to Killington as LA -Mammoth.
I would not say NYC supports late season skiing.
The diehards may be a tiny fraction of metro NYC/Boston, but of course that could still be enough to help make critical mass. Killington is another Powdr Corp purchase, and I predicted right away that spring would be curtailed based upon what happened at Bachelor. As at Bachelor there appears to be some rethinking this year.
I've talked to a few NYC skiers (my gf Liz has lived there for 25 years), and Killington is viewed by many as the drive limit for weekend trips. Many of them like Stowe and Sugarbush better but it's just too far to commute. Killington is the southern limit of the higher snowfall Vermont ski climate, and that intersection with the easier access from the big population centers makes it the logical choice for late season lift operations in the East.