From FB Messenger and phone conversation: A group (group 1) of sledders in the meadows of Tepee Basin witnessed an avalanche that failed an estimated 4 feet deep and up to one mile wide of the NE-facing wall that makes up the perimeter of Tepee Basin. They described the avalanche as breaking across the entire face, which, measured on Google Earth, is over a mile wide.
A second group (group 2) was riding higher in the meadow. We suspect that group remotely triggered the avalanche.
Group 1 confirmed that group 2 was clear and they got out their beacons to confirm no one else was captured.
From FB Messenger (second group): "The whole skyline ridge went off this afternoon on the Tepee side. We may have triggered it with our tree riding below, but the whole thing let go about a mile wide."
Video overview: O. El-Zaru