Date of Observation: 03/22/2023
Name: Eric Murrow
Zone: Southeast Mountains
Route Description: Snodgrass TH up standard skinner with detours to nearby steep terrain features.
Observed avalanche activity: Yes
Avalanches: I remotely triggered two avalanches on a southeast-facing feature below treeline; slides ran on the melt/freeze crust at the storm interface in low density storm snow from the start of the storm. I ski-cut a large Storm Slab that broke on a mid-storm weak layer on an east aspect; as the avalanche ran it propagated wider and down to the storm interface. This avalanche may have collapsed the soft melt/freeze crust beneath the storm snow on east aspects.
Weather: Overcast skies with increasing winds during the day. Strong winds penetrated down to valley bottom during the afternoon. Storm totals ranged from 20-22 inches. From 1030 to 130 snowfall rates were commonly in the 1 to 2-inch-an-hour range. Visibility was obscured all day so I never got a view of the surrounding terrain.
Snowpack: Avalanches in the storm snow were very easy to trigger with some occurring remotely. Low-density snow from the start of the storm remains sensitive to human triggers in sheltered areas. South and southwest-facing slopes below treeline had thick melt/freeze crusts around 4 inches thick below the storm snow and did not appear to cause concern for collapsing. Southeast and east-facing slopes crusts were thinner and may pose a threat for triggered avalanches after issues in the storm snow settle out. I experienced one collapse on an east-facing slope and a nearby test profile suggests that the crust below the storm snow is near its breaking point. I initiated a Loose Dry avalanche down a north-facing slope that gathered a lot of mass, but surprisingly, it failed to release a slab (maybe this slope avalanches the day before). Faceted grains were obvious beneath the storm snow in a north-facing test profile but no propagating results.
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- This avalanche, on southeast slope, was triggered from where photo was taken. It failed in low-density snow at the base of the storm snow.
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- Easy Shovel Tilt Test results the failed in the middle and bottom of the storm snow.
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- A long shooting crack triggered remotely. This was common during heavy snowfall rates around noon.
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- A look at the crown on a southeast slope. This avalanche ran above the crusts, but it seems like the crust below the storm snow could collapse as more accumulates tonight or on drifted terrain.
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- I was surprised that this Loose avalanche did not trigger a slab on this north-facing slope. Maybe this slope avalanched earlier in the storm and I was able to tell. I sure wouldn’t trust this result. The volume entrained in the Loose avalanche was easily large enough to catch and carry a skier.
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- A ski cut released this avalanche in the middle of the storm snow. As the avalanche ran, it released a slab at the base of the storm snow and propagated wider. Poor visibility and dangerous hangfire prevented me from investigating the deeper avalanche further down slope.
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- A quick look at propagating result on an east-facing slope. This failed below the melt/freeze crust. I dug here because I experienced an audible collapse nearby.
