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.
Photos:
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[accordion_item title=”Avalanche Report #1″ parent_id=”my-accordion” open=”false”]Estimated avalanche date: 03/22/2023
Number of Avalanches: 2
Location
Location: Snodgrass
Location Specific:
Start Zone Elevation: BTL: Below Tree Line
Aspect: SE
Characteristics
Trigger: Skier
Trigger modifier: Remote
Type: Soft Slab
Failure Plane: New/Old interface
Size
Relative Size: R2 small
Destructive Size: D1.5
Avg. crown height (inches): 20
Avg. width (feet):
Avg. vertical run (feet):
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Surprised by the distance on these remote triggers…200 feet. No audible collapse and crusts did not appear to collapse.
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[accordion_item title=”Avalanche Report #2″ parent_id=”my-accordion” open=”false”]
Estimated avalanche date: 03/22/2023
Number of Avalanches: 1
Location
Location: Snodgrass
Location Specific:
Start Zone Elevation: BTL: Below Tree Line
Aspect: E
Characteristics
Trigger: Skier
Trigger modifier: Controlled
Type: Soft Slab
Failure Plane: New/Old interface
Size
Relative Size: R2 small
Destructive Size: D2 – could bury, injure, or kill a person
Avg. crown height (inches):
Avg. width (feet):
Avg. vertical run (feet):
Involvements
# of people caught:
# of partial burials:
# of full burials:
Additional comments: Avalanche initiated mid-storm but as it ran pulled out a wider slab at the storm interface.
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