On the west side of Henderson Moutain, while ascending a low-angle slope toward a known avalanche path, we experienced several collapses. Halfway up the slope, Ian noted snowballs rolling down the hill and around the corner, we could see the debris that had come from the steep terrain above. We had a clear view of this slope near the snowmobiles and it had not avalanched when we began ascending. At some point from several hundred feet away, we remotely triggered the slope. The avalanche was ~150' wide, 2' deep and ran almost to the road. Across the gully, we could see large cracks but the slope did not avalanche. Above, cracking and collapsing continued and we got a view into the upper part of the gully and saw another crown of an avalanche that likely happened at the same time as the slope below.