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Avalanche Forecast

Archived

Dec 6th, 2021–Dec 7th, 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.

Regions

South Rockies.

Wind affected and loose snow have bonded poorly with the rain crust. Approach wind loaded features like ridge crests with caution, and manage your exposure to terrain traps in sheltered terrain where loose snow could run faster and further than expected. 

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

MONDAY NIGHT: Cloudy overnight with flurries possible. Moderate westerly winds. Freezing levels at valley bottom.

TUESDAY: Partly cloudy with no snowfall expected. Strong northwest winds, freezing levels at valley bottom. Alpine highs of -9. 

WEDNESDAY: Snow returns Tuesday night with up to 10cm expected by Wednesday afternoon. Winds increase to strong westerlies. Freezing levels rise to 1000m, alpine highs of -5. 

THURSDAY: Light snowfall continues, with light westerlies. Freezing levels below 500m.

Avalanche Summary

On Sunday, loose dry avalanches were observed out of steep sheltered terrain features. Size 1-1.5 wind slab avalanches were observed in immediate lee features at ridge crest. 

Small avalanches will move quickly on the crust bed surface. Be mindful of what is below you, such as cliffs and gullies, especially in steep terrain. 

Note there are very few field observations this early in the season. If you venture out into the mountains, please share your observations and/or photos on the Mountain Information Network!

Snowpack Summary

15-30cm of low density snowfall sits over a thick and supportive crust, on all aspects below 2400m. Moderate to strong westerly winds continue to redistribute this new snow into deeper deposits in lee features in the alpine and treeline. 

The mid November crusts sit 20-40cm above the ground below 2300m. Last week's heavy rain saturated the snowpack and has begun to break down this crust at treeline and below, creating a cohesive lower snowpack.

Snowpack depths range from 10-80 cm at treeline elevations. The snowpack tapers quickly below 1900m, significantly diminished by the rain event.

Terrain and Travel

  • Keep in mind the crust offers an excellent bed surface for avalanches.
  • Wind slabs may be poorly bonded to the underlying crust.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.

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.