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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.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia.

Isolated wind slabs may lurk around ridges and steep alpine features. Be mindful that travel may be the most hazardous part of your day.

Confidence

Moderate - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

SATURDAY NIGHT: Mostly cloudy with isolated flurries. West-northwest wind, 20-30 km/hr. Alpine low temperature -18 C. Freezing level valley bottom. 

SUNDAY: Partly cloudy and isolated flurries transitioning to sunny breaks. Decreasing northwest-west wind, 10-25 km/hr. Alpine high temperature -10 C. Freezing level valley bottom. 

MONDAY: Mix of sun and cloud. Light and variable wind 10-15 km/hr. Alpine high temperature -10 C. Freezing level valley bottom. 

TUESDAY: Sunny with increasing cloud cover. Southwest wind 10-15 km/hr. Alpine high temperature -8 C. Freezing level valley bottom. 

Avalanche Summary

On Thursday, Dec 2, a couple of cornice triggered avalanches were reported in the north end of the forecast region. A very large (size 3) deep persistent avalanche failed on a north aspect in steep, rocky alpine terrain on a crust from the start of November. The other cornice failure triggered a large (size 2.5) storm slab with an 80 cm crown on a steep southeast aspect in the alpine.

The recent series of atmospheric rivers onslaught brought heavy precipitation, strong winds, and warm weather. Widespread and very large natural avalanche cycles (up to size 3) were observed following each wave of storms, with avalanches frequently running full path to valley bottom. No new natural avalanches have been reported since Dec 1. Hard frozen debris will likely be found in the runout of most avalanche paths.

Snowpack Summary

10-30 cm fresh snow covers a supportive crust which has been found as high as 2400 m. Winds have exposed the crust in open areas and built wind slabs in leeward terrain, loose snow persists in protected areas and depressions. 

Below the surface crust, the snowpack is generally well-consolidated with a few early season crusts. The mid-November crust is found down 70-150 cm with faceting below the crust. This feature disappears above 1900 m.

Snowpack depths range from 100-250 cm at treeline and above. Below 1600m the snowpack decreases rapidly.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs 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.