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Avalanche Forecast

Archived

Dec 2nd, 2021–Dec 3rd, 2021

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

Keep your head up as you transition into wind effected terrain at higher elevations in the search for dry snow. Give wind loaded features time to gain strength from the latest round of stormy weather.

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

The atmospheric river has finally left the building! The Columbia's will be dry and cold until Saturday morning when an active pattern returns.

THURSDAY NIGHT: Clearing skies as flurries taper off. Winds ease to moderate westerlies. Temperatures drop, with freezing levels falling to valley bottom.

FRIDAY: Cold and partly cloudy with alpine highs around -7. Freezing levels stay below 1000m with light to moderate westerly winds.

SATURDAY: Light accumulations with increasing westerly winds. Freezing levels remain below 1000m with alpine highs of -7.

SUNDAY: Briefly clearing skies before snow returns Monday. 

Avalanche Summary

Size 1 loose wet and storm slabs were produced using explosive control methods near Revelstoke yesterday. Nearby Glacier National Park observed a widespread natural avalanche cycle and produced up to size 3.5 avalanches with explosive control. 

The last week of heavy precipitation, strong winds and warm weather has consistently produced multiple cycles of avalanche activity up to size 3. Widespread natural cycles were observed following each wave of the storm, with avalanches frequently running full path to valley bottom. Explosive control work on the highway corridors near Revelstoke produced similar significant results. Human triggered avalanches have been observed to size 1.5 in wind loaded features at alpine and treeline. 

Snowpack Summary

Strong southwesterly winds have redistributed recent storm totals of up to 120mm into deeper deposits at treeline and above. At lower elevations a melt freeze crust sits at the snow surface, over refrozen wet snow to ground.

The mid-November crust is up to 5cm thick and found down 70-150cm with faceting below the crust. The lower snowpack contains several early season crusts which appear well bonded.

Snowpack depths exceed 250cm at treeline and alpine elevations, while below 1600m the snowpack decreases rapidly with elevation. 

Terrain and Travel

  • Be especially cautious as you transition into wind affected terrain.
  • Stay off recently wind loaded slopes until they have had a chance to stabilize.
  • Carefully monitor the bond between the new snow and old surface.
  • Approach lee and cross-loaded slopes with caution.

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.