March 31, 2023

East River area and small skier triggered avalanche on drifted BTL slope

Date of Observation: 03/30/2023
Name: Eric Murrow

Zone: Southeast Mountains
Route Description: Traveled above the East River just up valley from the confluence with Brush Creek.

Observed avalanche activity: Yes
Avalanches: One slab avalanche that ran in the upper snowpack that likely failed during warming a few days ago on low elevation east slope. Intentionally triggered a Windslab on a small northwest-facing slope near valley bottom, this feature has an abnormally huge fetch. Wind Slab was resting above 1mm facets above a crust.
Weather: Mostly cloudy skies with moderate winds through 2pm. Snowfall and strong SSW winds started around 3pm.
Snowpack: HS through this low-elevation terrain typically ranged from 90 to 120cm outside of drifted terrain. A quick profile on a south-southeast slope at 9,100 feet showed a strong structure with ice columns to the ground which indicated meltwater has made its way through the entire snowpack (this strong structure is not common throughout the greater forecast area). A profile into the bed surface of the intentionally trigger slide, on a drifted northwest slope, showed a 10″ thick crust/ice column matrix resting about 2 feet of depth hoar. Surface conditions on northerly features were a thin melt/freeze crust with 6 inches of faceted snow below.

Photos:

A strong snowpack with meltwater forming ice columns to the ground.

A relatively weak snowpack on a low elevation northerly slope. Upper snowpack was a matrix of crusts and ice columns with faceted snow at the surface capped by thin melt/freeze crust.

Crown of triggered avalanche. Stiff, wind-drifted snow comprised the slab resting on a layer of facets which easily slid on the crust below.

A look up at the triggered avalanche. Behind this slope is a miles long open fetch area where the wind can gather snow.

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Estimated avalanche date: 03/30/2023
Number of Avalanches: 1

Location

Location: Other: Add text
Location Specific: Hills above East river just upstream of confluence with Brush Creek
Start Zone Elevation: BTL: Below Tree Line
Aspect: NW