Quick report
- Slope Angle
- 45°
Avalanche
- Slab Width
- 9 m
- Weak Layer
- Depth Hoar
- Trigger Type
- Skier
- Vertical Fall
- 183 m
- Avalanche Type
- Soft Slab
- Slab Thickness
- 91 cm
- Trigger Detail
- Unintentionally Triggered
- Start Zone Aspect
- Northwest
- Avalanche Problem
- Persistent Weak Layer
- Start Zone Elevation
- 2896 m
Forecaster Greg Gagne was in Porter Fork two days prior to the accident on Dec 6th. His observations can be found here: https://utahavalanchecenter.org/observation/40937 Another avalanche professional reported seeing a remotely triggered avalanche in nearby terrain (albeit at a much lower elevation) on Dec 2. https://utahavalanchecenter.org/avalanche/40765
Avalanche professional Nat Grainger's take on the snowpack from nearby terrain on Dec 3 in the video below -
Forecaster comments: We are glad this ended with only some bumps, bruises, lacerations, and a broken ski. This must have been a terrifying ride, rocketing down 40°-plus terrain and through younger stands of fir and spruce. Hats off to the team to self-evacuate. Same goes for reporting the incident. These incidents and stories help to keep others educated and hopefully safe.---------------------------- If the party is reading this, we would very much appreciate hearing more of the story. Best - Drew Hardesty drew@utahavalanchecenter.org------------------------------------------------ Thanks - Thanks also to Paul Diegel, Ashley Patterson, and Peter Donner for their help in this investigation.
Incident
- Number Caught
- 1
- Number Carried
- 1
- Number Injured
- 1
- Terrain Summary
- <p> </p> <p>The east chute in the Icebox is a very steep, rocky chute in the upper reaches of main Porter Fork in Mill Creek Canyon. It lies just slightly north and west of Peak 9661' and a little more than a half-mile west-northwest of Mt Raymond. The starting zone at 9550' faces north-northwest, exceeds 45° in steepness and is jagged, rocky terrain. The avalanche path itself, slicing through mature timber, runs for nearly 1000' as a narrow gulley, or tube, whose origins lie in an extreme avalanche event from an unknown cycle. The runout zone consists of younger timber and a lone, well-flagged mature fir. </p>
- Weather Summary
- <p>Early October snowfall and subsequent high pressure set the stage. The October snow, experiencing significant temperature gradient metamorphism, quickly devolved into loose, weak, sugary, faceted snow. By mid-November, we had a good potential bed surface in the way of crusts....good weak layers in the form of weak faceted snow.....all we needed were storms to build a slab to make avalanches. An active weather pattern began on Thanksgiving (November 22) through December 4th adding 61" of snow (5.14" snow-water-equivalent). (Snow and water numbers from Alta ski area. The Porter Fork area typically has 50-75% of this snow.) This, combined with periods of stronger winds, led to unstable avalanche conditions with a High or Considerable avalanche danger for suspect terrain through Dec 8th. </p> <p>Greg Gagne's Week(s) in Review can be found <a href="https://utahavalanchecenter.org/blog?uid=43&fbtv=Week%20In%20Review&m=All&y=All">here.</a> </p>
- Number Partly Buried
- 1
Party's report in italics: Second skier on the slope was caught. Slope broke above the skier, right where you would expect it to near some rocks on the entrance of the chute after the skier was a good 100' below. Skier was dragged through some trees before coming to rest with head and arms above snow and facing downhill. Both skis were recovered, but one was split in half. We were able to self evacuate, but the caught skier suffered a facial laceration that required a trip to the ER, bruised hip, back and shoulder.
Despite the broken ski, the injured party was able to self-evacuate by post-holing over 3 miles and 3500' vertical back to the Porter Fork parking.