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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

Lizard-Flathead.

New snow will improve riding quality but bond poorly to the underlying crust. Although the anticipated size of avalanches is small, they will likely be quite 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 3 cm of new snow accumulation. Freezing levels lowering to valley bottom. Winds ease from strong westerlies to light to moderate from the northwest. 

Sunday: Partially cloudy in the morning with isolated flurries, clearing in the afternoon. Light westerly winds with freezing levels at valley bottom.

Monday: Cloudy with flurries, up to 3 cm of accumulation. Moderate to strong northwesterly winds. Freezing levels at valley bottom.

Tuesday: Partially cloudy with isolated flurries. Strong northwest winds at ridgetop, freezing levels at valley bottom. 

Avalanche Summary

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

If you head out this weekend, 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. Above 2400m, strong to extreme winds have created a variety of wind-affected surfaces. Westerly winds will have redistributed this new snow into wind slabs in the alpine and treeline.

Previously, the mid-November rain crust could be found near the base of the snowpack. It is likely that rain has begun to break down this crust at treeline and below, and amalgamated the lower snowpack into melt forms with a thick capping rain crust above.

Snowpack depths range from 10-80 cm 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.
  • Be careful as you transition into wind affected terrain.

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.