Avalanche
- Slab Width
- 18 m
- Weak Layer
- Facets
- Trigger Type
- Skier
- Vertical Fall
- 91 m
- Avalanche Type
- Soft Slab
- Slab Thickness
- 25 cm
- Trigger Detail
- Remotely Triggered
- Start Zone Aspect
- North
- Avalanche Problem
- Persistent Weak Layer
- Start Zone Elevation
- 3078 m
Two slides are visible from the road through the Town of Alta on Baldy shoulder. One slide is in "the armpit," and the other in "Bounous' Chute." Dimensions are tough to estimate from the road but they look like they're each ~60 wide, and most likely failed on the extremely weak, 2-3mm facets present on high north prior to yesterday's graupel and last night's medium density snow. The slides are likely ~10 inches deep, given a storm total of ten inches at the nearby collins study plot. From the road, it is not possible to tell whether there are any tracks into, out of, or anywhere near the slides, although there are people skiing around at Alta today.
Forecaster Note:
While the weak layer of these slides cannot be determined with 100% accuracy by viewing them from a distance, a faceted weak layer is a distinct possibility. Below is a photo from Sunday's Observation which shows that the starting zones of these avalanches had snow cover prior to the storm. Being that almost all of the snow on the northerly aspects that I've looked at is faceted, it is quite likely that these failed on a faceted weak layer. This is very pertinent information given our current situation and we will work on confirming this.
Updated 10-29-2013 - 5pm
Patroller Cawley and I went up and confirmed faceted snow as the weak laye.
Kobernik
UPDATED 10-30-2013
More information was submitted by Jim M and it appears that these were most likely remotely triggered by skiers on the ridge from quite a distance away.
"Some additional info on Collins Gulch... Partner & I went up Baldy Shoulder to observe snow pack with very little hope of skiing it. The higher we got, the less & less the snow behaved. Stayed on low angle terrain and were experiencing collapsing and lots of far running cracks. Retreated back down our up track and on the way down, noticed two slides that were not there on the way up. Thinking we possibly triggered them remotely seeing the cracking & plenty of energy in the snow pack. All it needed was enough of an angle to move. Plenty of dirty snow & facets for the new snow to move on."
Photo - Jim M