Avalanche Forecast

Issued: Jan 1st, 2020 2:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Storm Slabs and Persistent Slabs.

Avalanche Canada jfloyer, Avalanche Canada

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A fine day Thursday before another storm rolls in on Friday. A weak layer lurks below the surface, so cautious terrain selection is required.

Summary

Confidence

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

Weather Forecast

Wednesday night: 4-8 cm new snow with strong westerly ridgetop winds. Freezing level lowering to valley bottom.

Thursday: Dry, with a mix of sun and cloud. Strong northwesterly winds. Treeline temperatures around -12°C.

Friday: 15-20 cm new snow with rain at lower elevations. Freezing level around 1600 m. Strong southerly winds.

Saturday: 10-15 cm new snow. Freezing level lowering to valley bottom. Strong southwesterly winds. 

Avalanche Summary

A wide, but relatively thin avalanche that involved a skier was reported from the Farm on December 29: https://www.avalanche.ca/mountain-information-network/submissions/a38b031a-7845-48fd-acdb-a0c00e9e2339. A similar event was reported from Pine Pass: https://www.avalanche.ca/map/forecasts/north-rockies?panel=mountain-information-network-submissions/4fc391f2-81cc-4725-a960-b2d71388ba70. These and several other avalanches reported Dec 29 to Dec 31 appear to have failed on a layer of surface hoar buried 30-40 cm below the surface.

Snowpack Summary

A weak layer of feathery surface hoar is buried around 40 cm below the surface. Avalanches have already been reported to have run on this layer and it is also showing "sudden" reactivity in snowpack tests. It is still at a burial depth where further storms will most likely increase, rather than decrease its reactivity.

There are a pair of weak layer in the middle of the snowpack. One is a surface hoar layer that appears to be gaining strength. The other is a layer of facets that lies above a relatively thin crust. Both these layers appear to be gaining strength.

The lower snowpack contains several crust layers, which could be a concern in shallow areas along the eastern slopes of the region.

Terrain and Travel

  • Choose conservative terrain and watch for clues of instability.
  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.

Problems

Storm Slabs

An icon showing Storm Slabs

Storm slabs will form once again with Friday's weather system. Good amounts of new snow and wind with rising temperatures will make avalanches very likely on Friday.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Very Likely

Expected Size

1.5 - 2.5

Persistent Slabs

An icon showing Persistent Slabs

A surface hoar layer is buried around 40 cm below the surface. New snow or the weight of a rider could easily trigger avalanches on this layer.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1.5 - 2.5

Valid until: Jan 3rd, 2020 5:00PM