Avalanche: Rock Canyon

Location

United States
40° 15' 52.8012" N, 111° 36' 49.9824" W
Observer Name
Dave Jarvis
Observation Date
Sunday, March 3, 2013
Occurrence Date
Sunday, March 3, 2013
Occurence Time
Afternoon

Region:

Location Name or Route
Provo Rock Canyon Trail
Elevation
6500
Aspect
North
Slope Angle
Unknown
Trigger
Unknown
Avalanche Type
Wet Slab
Avalanche Problem
Wet Slab
Weak Layer
Facets
Depth
unknown
Width
100
Vertical
Unknown
Comments
Coming down Rock Canyon at 1pm I heard a couple short rumbles that sounded like they were from the large rocky bowl on the north face of Y Mountain. I could see a patch of lumpy debris, but because of flat light I couldn't confirm newness or its start area. Sky was heavy overcast to roughly 8000', it was misting. the Cascade Snotel recorded 35-36 degrees but I think it was at least a couple of degrees warmer in the lower Rock Canyon area.
Comments
About a mile east of the trailhead, there is an area where the north aspect rises steeply from the trail. Avalanches have repeatedly come down this section since around Christmas. When I reached that point there had been one or two avalanches that had run, adding to previous debris. The debris was damp, large-scaled mashed potatoes. A lot of the snow was in the bowling ball to 20" size. Some swept onto and past the use-trails that cross the older debris pile. One lump on the trail was nearly 24" diameter. Up slope, there were a few areas scoured to the ground. The use-trails are off-camber and slick. I wouldn't want to have been crossing when it came down. I estimate that it came down 12-12:30pm. (this is the pushpin location on the map)
Comments
About 200 yards up from the second gate I heard, then saw another avalanche about 800-1000" up the south side of the canyon. The debris cascaded down two 150" falls in an area of vertical rock. The area it was in does have potential to run to the trail. It also has enough sunlight from the west that dry ground probably stopped the debris.
Map
40° 15' 52.8012" N, 111° 36' 49.9824" W