Another group that was in Triangle bowl at the same time reached out to us via Instagram to share some additional info. Their estimation of the size of the avalanche in Triangle bowl was roughly the same size as reported by this group. Thanks to Warren Gage for sharing additional details and photos.
We've also received word of two other large snowmachine-triggered slides on Seattle Ridge near Widowmaker and Little Sweeden. More details and photos: https://www.cnfaic.org/observations/seattle-ridge-132/