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Archived

Avalanche Forecast

Dec 30th, 2019–Jan 1st, 2020
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
3: Considerable
The avalanche danger rating below treeline will be considerable
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: North Rockies.

A reactive layer of surface hoar combined with stormy weather is expected to result in avalanches in the mountains this week. Have fun, but be cautious in your terrain selection over New Year! 

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Monday night: Up to 30 cm new snow is possible for areas to the south of the region. The north will see more like 10-15. Southwesterly winds 60-80 km/h. Freezing level around 1200 m.

Tuesday: 5-10 cm during the day with another 10-20 cm Tuesday evening. Strong southwesterly winds. Freezing level around 1300 m.

Wednesday: 10-15 cm new snow. Strong southwesterly winds. Freezing level around 1100 m.

Thursday: lingering flurries in some places. Moderate or strong westerly winds. Freezing level dropping to valley bottom, temperatures lowering to around -10°C at treeline. 

Avalanche Summary

A large, but relatively thin avalanche that involved a skier was reported from the Farm on December 29: https://avalanche.ca/mountain-information-network/submissions/a38b031a-7845-48fd-acdb-a0c00e9e2339. This appears to have failed on a layer of surface hoar buried 20-30 cm.

Other small slab and loose snow avalanches were observed from the Torpy area on the same surface hoar layer.

A slab avalanche that released deeper in the snowpack, likely on a crust and facets near the base of the snowpack was observed on December 29 from the McBride area.

Snowpack Summary

A weak layer of feathery surface hoar is buried 20-30 cm below the surface, and will become further buried by expected new snow this week. This layer is already reactive and will likely become more reactive as more snow is added.

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

  • Dial back your terrain choices if you are seeing more than 30 cm of new snow.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Avalanche Problems

Storm Slabs

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1.5 - 2.5