Taking family up the trail and heard massive roaring and saw significant avalanche coming down north facing slope of the canyon on Mt. Timpanogos trailhead above sundance about the same spot where you run into the first waterfall up the trail (about 1 mile above beginning of trailhead). Snow did not come far down enough to cover trail but scary enough where my family and I felt compelled to run up the opposing slope for safety (we were about 200 hundreds below where the avalanche was, but it kept coming without letting up for about 15 seconds.