A party of two ascending high on the E ridge of Superior triggered a wet slab avalanche @ ~2 pm today. The slide was apparently sympathetic to a couple rollerballs, and it stepped down to the most recent brown snow, probably the MF crust from prior to the 4/11 storm. The crown looked to be about a foot deep and about 20'-40' off the ridge. It spanned most of the broad ridge in between Superior and Little Superior, probably 100' feet wide, entraining lots of dirt and rock, and running halfway down the lower apron of Superior. It's worth noting that the hourly average temperature at the base of Alta Ski Area between 1 and 2 pm today was 69 degrees.