Avalanche: Collins Gulch

Location

United States
40° 34' 21.3528" N, 111° 38' 25.3068" W
Observer Name
Cawley
Observation Date
Tuesday, October 29, 2013
Occurrence Date
Tuesday, October 29, 2013
Occurence Time
Unknown

Region:

Location Name or Route
Baldy Shoulder
Elevation
10100
Aspect
North
Slope Angle
Unknown
Trigger
Skier
Trigger: additional info
Remotely Triggered
Avalanche Type
Soft Slab
Avalanche Problem
Persistent Slab
Weak Layer
Facets
Depth
10"
Width
60
Vertical
300
Comments
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.
Comments

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

Comments

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
 

Map
40° 34' 21.3528" N, 111° 38' 25.3068" W