This was one of two avalanches triggered by snowmobilers within about 300 feet of each other. It was up to 4' deep in the deepest location.
The Fish Lake Region has some quite weak snow from the ground up to around 18" above the ground. The recent storm added enough weight in wind loaded areas to create a danger to motorized users who might venture into this terrain. In most areas, this weakness is not reactive right now. It appears that you need to be in an area that has additional snow from the winds, in other words, you need a slope that has been drifted in pretty deep on top of this weakness. The weakness is most pronounced on west through north through east facing slopes. The new wind loads are primarily on the more easterly facing slopes. The slopes need to be over 35 degrees in steepness.