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Observation: Turnagain

Location: Sunburst

Date:
Observer:
Route & General Observations

Ascended and descended the Sunburst uptrack to 3100′. Our objective was to catalog what has avalanched, continue to observe the extent of the deep slab problem, and observe where wind slabs were located and how reactive and connected they were.

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Observer Comments

None observed

Weather & Snow Characteristics
Please provide details to help us determine the weather and snowpack during the time this observation took place.
Weather

Sunburst parking lot at 1200: 16 F, clear, calm winds, no precip, valley fog
3100' at 1300: 17 F, clear, light winds from the SE, no precip
Sunburst parking lot at 1545: 10 F, clear, calm winds, no precip,

Snow surface

The recent winds have scoured most places along the ridge down to the old melt freeze crust, while forming wind slabs ranging in size, and up to 5" thick in some areas. The conditions are very firm in the alpine, peppered with pockets strastrugi here and there. At and below alder line a wind crust ranges in size from 1-2" thick. Everything is covered by around 1 inches of faceting decomposing particles and intact surface hoar ranging from 2-6 mm in size (increasing in size with elevation).

Snowpack

Below alder line, the 1-2" wind crust sits above facets, on top of an extremely stout melt freeze layer.

Above alder line, the snow pack varies in depth and structure depending on where it has been scoured down to an old melt freeze crust on the surface, or where it has been loaded with a wind slab up to 5" thick or sculpted in waves of strastrugi. Generally, we found fewer wind slabs and more melt freeze at the surface. At ~2500' we dug down and the structure generally consisted of surface hoar over a thin layer of faceting decomposing particles over a melt freeze crust over facets over a thick slab to basal facets on the ground. In some leeward areas a wind slab sitting over facets lied between the surface hoar and melt freeze crust. Hand pits were difficult to isolate due to the stiffness of the melt freeze crusts, but were consistently failing on isolation on the facets underlying the wind slab or melt freeze crust.

A pit dug at 3100' exhibited poor strength, low propagation potential, poor structure. The pit profile is shown below in pictures.

Photos & Video
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