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Avalanche Forecast

Archived

Jan 9th, 2021–Jan 10th, 2021

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

Regions

Sea To Sky.

It may be tempting to get into bigger terrain, however high consequence persistent slab avalanches continue to be reported every few days. The best and safest riding will be found in mellow wind sheltered terrain. 

Confidence

Low - Uncertainty is due to unpredictable avalanche behavior.

Weather Forecast

Saturday Night: Flurries, accumulation 5-10 cm, moderate southwest wind, alpine high -5, freezing level 700 m.

Sunday: Mainly cloudy with flurries, accumulation 5-10 cm, moderate southwest wind, alpine high -3, freezing level 900 m.

Monday: Snow, accumulation 10-20 cm, moderate to strong southwest wind, alpine high -1, freezing level 1300 m.

Tuesday: Snow or rain, moderate to strong southerly wind, alpine high 0, freezing level 1600 m.

Avalanche Summary

Late Saturday there was a report of size 3 skier triggered avalanche at treeline on a westerly aspect on Cowboy Ridge. Details are limited at this time.

On Thursday there was a report of a remotely triggered (from a distance of 20m) size 2.5 deep persistent slab avalanche on a west aspect at 1930 m on Cowboy Ridge. The fracture line was up to 200 cm deep. This avalanche subsequently triggered an additional size 2.5-3 deep persistent avalanche about 50 m below.

On Wednesday there were numerous size 2 explosives controlled storm slab avalanches reported running in the alpine and treeline. As well there were several persistent and one deep persistent slab size 2.5-3 ranging in depth from 100-150 cm.

Snowpack Summary

Storm snow from the past week has seen extensive wind effect at upper elevations, with scoured windward aspects, wind slabs in lee features and growing cornices at ridgetop.

The snowpack is currently quite complex. The layer of greatest concern is a melt-freeze crust from early December, found around 100-200 cm deep in the snowpack. This crust may have surface hoar or sugary faceted grains sitting above it. There have been several recent large natural and human triggered avalanches on this layer and large loads have potential to trigger these layers. Near the base of the snowpack there are facets sitting on a crust from early November which have been identified as the failure layer in recent sporadic large avalanche releases.

Terrain and Travel

  • Be careful as you transition into wind affected terrain.
  • Make conservative terrain choices and avoid overhead hazard.
  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Cornice failure may trigger large avalanches.

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.