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Avalanche Forecast

Archived

Feb 10th, 2021–Feb 11th, 2021

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Northwest Inland.

Wind and extreme cold is not a fun combo! Be mindful of wind loaded features and use a conservative mindset when planning objectives in these temperatures.

Confidence

Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack. Uncertainty is due to the limited number of field observations.

Weather Forecast

WEDNESDAY NIGHT - Cold / light to moderate east wind / alpine high temperature near -30

THURSDAY - Still cold, but still sunny / light to moderate east wind / alpine high temperature near -24

FRIDAY - A mix of sun and cloud / light east wind / alpine high temperature near -17

SATURDAY - Cloudy, trace of snow, light south east wind / alpine high -13

Avalanche Summary

Suspect there is continued snow transport building slabs with the recent variable wind. A Feb 9th MIN observation shows some stiff wind affected snow over sugary facets.

Evidence of recent natural wind slab avalanches (likely occurring Saturday) were observed on Sunday as discussed in this MIN report. Small loose dry avalanches were also reported, in some cases likely triggered by the sun.

As the recent low-density snow becomes more consolidated and forms a slab, the likelihood of avalanches may increase.

Snowpack Summary

Cold temperatures are encouraging surface faceting and variable winds are impacting loose snow. The late January interface is down 30-50 cm, consisting of isolated surface hoar in sheltered locations, and previous wind effect in exposed areas. On solar aspects, a buried sun crust can be found below 1000 m. 

The lower snowpack has two decomposing crust layers. The upper crust is 70-140 cm deep and continues to show occasional hard, sudden results in snow pits. The deeper crust at the bottom of the snowpack is more prevalent in shallow snowpack ranges. These deep persistent layers seem to be dormant under the current conditions, but shallow rocky slopes should still be carefully assessed and approached with caution. 

Terrain and Travel

  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.