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Avalanche Forecast

Archived

Dec 5th, 2021–Dec 6th, 2021

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

Regions

South Rockies.

Recent snowfall is bonding poorly with the underlying crust. Avalanches will move fast on this smooth surface. Be cautious in steep terrain above cliffs and terrain traps, and in wind loaded features. 

Confidence

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

Weather Forecast

SUNDAY NIGHT: Partly cloudy with moderate westerly winds at ridgetop with freezing levels at valley bottom.

MONDAY: Cloudy with flurries. Moderate to strong west-northwesterly winds easing into the afternoon. Freezing levels at valley bottom. Alpine highs of -10.

TUESDAY: Partly cloudy. West-northwest winds increase again, with freezing levels at valley bottom. Alpine highs of -8.

WEDNESDAY: Cloudy with light accumulations, freezing levels below 1500m. 

Avalanche Summary

Yesterday, 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. 

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

Snowpack Summary

15-30 cm of new snow sits on top of a thick rain crust on all aspects below 2400m. Westerly winds continue to redistribute the new snow into wind slabs in the alpine and treeline. 

Previously, early season crusts could be found in the snowpack below 2300m, 20-40cm above the ground. At lower elevations these crusts have likely begun to break down from the heavy rainfall, creating a cohesive refrozen snowpack with the thick rain crust at the surface. 

Snowpack depths range from 10-80cm at treeline elevations. Higher elevations may hold a deeper snowpack, but will also be more heavily impacted by recent winds. Rain has washed away the snowpack below 1900m. 

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.