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Avalanche Forecast

Archived

Dec 4th, 2021–Dec 5th, 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.

New snow will improve riding conditions, but bond poorly to the underlying crust. Although the forecasted size of avalanches is small, they will likely be reactive to human triggering.

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Saturday Overnight: Mainly cloudy with up to 5 cm of new snow overnight. Freezing level dropping to valley bottom. Moderate to strong southwest winds easing to light and shifting northwest.

Sunday: A brief ridge of high pressure over the Rockies. Flurries end in the early morning with skies clearing into the afternoon. Moderate westerly winds at ridgetop with freezing levels at valley bottom.

Monday: A cloudy start with up to 5 cm of new snow accumulation. Moderate to strong northwesterly winds easing into the afternoon. 

Tuesday: Partially cloudy with isolated flurries. Strong southwesterly winds increase to extreme in the late afternoon.

Avalanche Summary

No new avalanches have been reported in the past 24 hours.

If you go out in the mountains, please share your observations and/or photos on the Mountain Information Network! ?

Snowpack Summary

15-20 cm of new snow sits on top of a thick rain crust on all aspects below 2400m. In the high alpine (above 2400m) new snow overlies a variety of wind-affected surfaces. Westerly winds will have redistributed the new snow into wind slabs in the alpine and treeline. 

Previously, 2 early season crusts could be found in the snowpack below 2300m. It is likely that last week's rain has begun to break down these crusts, and amalgamated the lower snowpack into melt forms below the thick capping rain crust.

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

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

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.