Avalanche: Collins Gulch 11/6/2011

Observer Name: 
Kobernik
Observation Date: 
11/06/2011
Occurrence Date: 
11/06/2011
Occurrence Time: 
10:30am
Region: 
Collins Gulch
Little Cottonwood Canyon
Salt Lake
Location Name: 
Collins Gulch
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Location

40° 34' 23.232" N, 111° 38' 25.4616" W
Avalanche Characteristics
Elevation: 
10000'
Aspect: 
Northeast
Slope Angle: 
35
Trigger: 
Skier
Trigger: additional info: 
Unintentionally Triggered
Avalanche Type: 
Soft Slab
Weak Layer: 
Facets Above Crust
Depth (avg): 
12"
Width: 
15'
Vertical: 
50'
General Comments

This little slide is hardly much concern but make no doubt that it is a slab avalanche that failed on weak preexisting snow from October.  I was below at the time the skiers triggered it but I was looking away when it released.  I don't believe anyone was caught.

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General Comments 2

Of course, I had to go take a look at it because this preexisting faceted snow was exactly what was on my mind and what I intended to look at during the day anyway.  The debris was quite soft.  The pocket was probably just large enough to knock someone over with burial quite unlikely.

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General Comments 3

A view of the flank.  I performed an extended column test here at the crown face which propagated on 12 taps.

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General Comments 4

The structure is as follows from the ground up. 

On the ground sits 6 to 8 inches of snow from early October which underwent a number of melt freeze cycles but is starting to break down and facet.  In many locations this layer is fairly stout with a melt freeze crust present.

The next layer is from a couple of smaller storms that occurred in mid October.  These layers have become weak through the near surface faceting process over the last few weeks.  I found this layer to be weaker then I expected.  I have only looked at snow one other day so far this winter and the location I looked at had a thinner layer of facets that weren't as loose.

The newest snow sits on top of the facets.  For the most part the new snow is lower density and undisturbed from the wind which doesn't promote ideal slab formation.

BOTTOM LINE:  Conditions are not exceptionally dangerous right now and activity will be quite localized in areas above 9500' on the more northerly aspects.  Keep an eye out on slopes that are still holding snow from October.

How these layers behave in the future is another question.  These layers will no doubt be monitored closely over the next week.  With a ridge of high pressure in the weather forecast (mild weather in other words) I'd expect these layers to undergo more faceting and become at least somewhat weaker.

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