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Avalanche Forecast

Archived

Jan 11th, 2021–Jan 12th, 2021

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

Regions

North Columbia.

Avalanche hazard will gradually rise over the day and into Tuesday night as new snow and wind form fresh wind slabs at upper elevations. 

If you see more than 20 cm by the end of the day, treat avalanche danger as CONSIDERABLE at elevations with wind blowing the snow around.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

Monday night: Flurries, trace, moderate to strong southwest wind, freezing level 600 m.

Tuesday: Snow, 5-15 cm, strong southwest wind, alpine high -4, freezing level 1200 m.

Wednesday: Snow overnight then clearing, 10-20 cm, moderate northwest wind, alpine high -9, freezing level 1200 m.

Thursday: Sunny, light southwest wind, alpine high -7, freezing level 700 m with a weak inversion setting up.

Avalanche Summary

Isolated wind slabs have been occasionally reactive to skier traffic, limited to size 1.

Snowpack Summary

New snow falls on wind affected surfaces at upper elevations, surface hoar in wind sheltered areas and a thin crust on solar aspects. Winds are likely redistributing new snow into wind slabs and growing cornices. 

A couple of persistent weak layers exist in the upper to mid snowpack:

  • The upper layer, found 50-80 cm down, is a spotty layer of surface hoar at treeline and below. 
  • The lower layer, found 90-150 cm down, is widespread and can present as surface hoar and/or a crust.

Avalanche activity on these layers has dwindled since last week and snowpack tests results have been moderate to hard planar, but still showing some propagation. Incoming snowfall will add additional load to these layers and may shed some light on whether they will remain a concern.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs are most reactive during their formation.
  • Dial back your terrain choices if you are seeing more than 20 cm of new snow.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.