Observation: Turnagain

Location: Sunburst-Above Treeline

Route & General Observations

Standard approach breaking trail towards Sunburst ridgeline above treeline. Our focus was to assess the forecasted snowfall and its effect on the current snowpack. Though we started our tour with an obscured sky, strong NE winds and rapid accumulation (S-4), the winds, snowfall and sky opened up by 1pm. Widespread, LOUD whumphing from 2,000 ft to our high point of 2,400 ft where we conducted instability tests.

Red Flags
Red flags are simple visual clues that are a sign of potential avalanche danger. Please record any sign of red flags below.
Obvious signs of instability
Recent Avalanches?No
Collapsing (Whumphing)?Yes
Cracking (Shooting cracks)?Yes
Observer Comments

Cracks were localized and extended 2-20m from ski tips.
Whumphs were widespread from 2,000-2,400ft and occurring every 5-20 steps. Though some were small, we encountered auditory collapses that could easily pass for a mustang engine and an A-10 flying through the Valley. The collapses were approx 1-2 seconds in duration and spread in all directions. Simply fascinating.
No observed releases or slides.

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

Obscured skies trending to Broken between 11-2pm.
Strong NE wind around 11-12pm with a NE wind trending to light by 1pm.
-7°C to -5°C

Snow surface

Fresh Precip particles approx 2-4mm with active riming.
A right-side up fresh accumulation of approx 20-40cm existed from 1,500-2,400 ft.
No crusts were present until our exit, where a fragile surface crust existed in the meadows, possibly from the fall in temperature and previously falling moist snow.
Trees and alders in wind protected areas held approx. 5-10cm on branches.
Ski/Boot pen: 26mc/60cm


In general, our focus was to assess the forecasted storm accumulation and see the rapid loading first-hand. The early season setup of basal facets with rapid loading were undergoing artificial collapses every few steps and proved to be the layer of concern for our tests. In addition, the once proudly standing surface hoar has been flattened by this dense snowfall and though it produced results in CT and ECT’s, it seems in time it will become cohesive and fully bonded into the New/Old interface. The one main concern I have is we found striations and cups of depth hoar, leading me to believe the cold, clear week prior advanced the basal facet layer. Good focus for days to come.

2,000 ft, W , 21° Slope,
STE 40cm down on N/O Interface
CT11 SP (Simultaneous fractures)
20cm down within New interface
32cm down on buried surface hoar
48cm down on basal facets

Photos & Video
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