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Avalanche Forecast

Archived

Jan 3rd, 2022–Jan 4th, 2022

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 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.

Regions

North Columbia.

Reactive storm slabs are widespread at all elevations. Evaluate terrain features carefully. Avoid large unsupported slopes and navigate wind loaded features cautiously. 

Confidence

High - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

MONDAY NIGHT: Up to 10cm of snow overnight. Winds drop to moderate southwesterlies. 

TUESDAY: Chance of flurries with light southeast winds. Alpine high of -15. 

WEDNESDAY: Clearing skies, isolated flurries. Light southwest winds. Alpine high of -15. 

THURSDAY: Light snowfall begins early morning with increasing southerly winds. Temperatures begin to rise with an alpine high of -10.

Avalanche Summary

On Sunday, several natural and skier triggered slabs were observed in wind loaded features at treeline and above to size 2.

Cornice falls have triggered numerous slabs this week, as they land on the slope below. Navigate around cornices carefully, both on ridgelines and on the slopes below them with care - they are able to effect deeply buried weak layers. 

Several large and destructive persistent slab avalanches have been naturally and skier triggered in the over the last week up to size 3, failing on the early December crust/facet interface. Each had wide propagation and ran several hundred metres. The avalanches were all triggered in a rocky and thin area.

Snowpack Summary

Up to 40 cm of low density storm snow has fallen this week and has been redistributed into wind loaded features at treeline and above by strong southwest winds. 

A layer of weak surface hoar crystals can be found 30-50cm deep in sheltered terrain features at alpine and treeline elevations, and in open features like cut blocks below treeline.

The crust formed by the early December rain event sits 100-150cm deep and is found up to 2200 m. Faceted grains sit above, creating a weak interface that is still reactive to human triggers. This layer is most reactive at treeline in areas where the snowpack thins and the weak interface is much closer to the surface. This layer has the potential to produce large and destructive avalanches if triggered. Natural and skier triggered avalanches have occurred in this layer to size 3 in the last week.

Terrain and Travel

  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.