How about all the way through the spring, even on slopes that have been groomed and all bumped-up!
Scary details in this video:
And in the Gallatin Nat'l Forest avy bulletin:
"Bridger Bowl experienced their most impressive day of wet slab avalanche activity in memory. Avalanche cycles like this one are rare. It was only the second time in my 22 years of avalanche work that I’ve seen wet slab activity on this scale. Yesterday, the ski patrol triggered avalanches with explosives that gouged out groomed runs and road cuts plus put debris up to 20 foot deep in the gullies."As well as in the picture below from an Unofficial Networks article: