Avalanche: Porter Fork

Observer Name
Observation Date
Thursday, February 25, 2010
Avalanche Date
Thursday, February 25, 2010
Region
Salt Lake » Mill Creek Canyon » Porter Fork
Location Name or Route
Elevation
9,700'
Aspect
Northwest
Slope Angle
30°
Trigger
Skier
Trigger: additional info
Unintentionally Triggered
Avalanche Type
Hard Slab
Weak Layer
Surface Hoar
Depth
12"
Width
800'
Vertical
1,500'
Comments

Large avalanche triggered by skiers on the northwest face of Gobbler's Knob. No one caught. They were on the northwest shoulder of Gobbler's in the trees, which is very gentle, around 30 degrees when they triggered the avalanche and it propagated very wide across the face to the steeper (38 degree), center of the large, northwest face of Gobbler's. Width was reported between 250' by reporting party to 800' wide by other knowledgeable people in the area. It is very unusual to trigger avalanches on this very gentle, area with gladed trees, but this is a good example of the sensitivity and gentle slopes typical of avalanches on surface hoar. One person who was familiar with the history of the area said that they triggered the hangfire that did not slide during the February 15th event on the same slope.

Comments

Here is the email from the party that triggered the slide:

Skier triggered slide on Gobblers knob west shoulder, approach from porter fork. 250 odd feet crown, 1 and 1/2 feet deep that went for 1200 feet. Snow fell all day and winds were light but we did not go to the ridge of Gobs, surely the winds there were around 30mph. Soft slab, NW aspect, below 10,000ft, 1 1/2ft depth buried surface hoar, 30-32 degrees, ran for 1200 - 1400 ft. Skier triggered Did not see any settlement all day until the slide, no cracking, collapsing, we did ski cuts with no results, etc. We did not mess around on the wind deposited pillows towards the ridge. They were obviously new and sensitive medium density snow, large snow flakes were falling in great amounts The slide ran rather slowly allowing the skier to easily ski to a safe area, it was remote triggered and broke about 50 feet above the skier. Hoar frost from earlier weeks caused the slide apparently, we dug several hand pits and one test pit that sheared four inches and indicated no other weakness.

Comments

Photos by Andrea Sinclair

Coordinates