Avalanche Forecast

Moderate - Confidence is due to a stable weather pattern with little change expected. The snowpack structure is generally well understood. Uncertainty is due to the fact that deep persistent slabs are particularly difficult to forecast.

Monday Night: Mostly clear. No new snow expected. Variable light wind. Freezing level falling to valley bottom. Alpine low around -7 C. 

Tuesday: Partly cloudy. No new snow expected. Light west wind, trending to strong northwest at higher elevations. Freezing level rising to 800 m by the afternoon. Alpine high around -5 C.

Wednesday: Partly cloudy, possibly clear by the afternoon. No new snow expected. Light west wind, trending to extreme northwest at higher elevations. Freezing level at valley bottom overnight, rising to 600 m by the afternoon. 

Thursday: Mostly sunny. No new snow expected. Light southwest wind trending to strong northwest at higher elevations. Freezing level at valley bottom overnight, rising to 500 m by the afternoon. 

On Monday, a professional operation near the Glacier National Park boundary reported a natural size 3 avalanche in steep, wind-loaded terrain.

 

On Sunday, a professional operation west of Panorama reported a size 2.5 natural windslab avalanche that appeared to have been triggered by a falling cornice. It was on a south aspect in the alpine.  

On Saturday, a several rider triggered wind slab avalanches up to size 2 were reported near Golden. They were on north through southeast aspects at treeline and above. See this Mountain Information Network post for pictures and more information about one of them. 

Additionally, west of Invermere, a small, rider triggered avalanche was reported to have failed on the early December persistent weak layer. The snowpack may be shallower in this location, making this layer easier to trigger, but it's a good reminder that this crust/facet combo is still active.

Over the last week, the early December persistent weak layer has produced a few large natural avalanches (2-3) in the center of the region. Explosive controls have also produced a few size 2 avalanches that failed on the same persistent weak layer, one being remotely triggered. These occurred on thin to thick features on northeast-facing slopes from between 1600 m and 2000 m, where the layer was buried 100 cm + deep. 

Professional operations across the region are reporting surface hoar growth from 2 mm all the way up to 12 mm, and a thin crust on steep solar aspects in areas that saw the sun on Friday or Saturday. In the far northern end of the region, the surface seems to be mostly wind effected.

Up to 10 cm of recent snow and strong winds have formed pockets of reactive wind slab, especially where it sits above surface hoar and crusts.

Around 1900 m and below, a crust is now capping the dense 10-30 cm of snow which has settled significantly with the past mild temperatures. The crust varies from thin to thick, according to the aspect and elevation. Below this, a layer of surface hoar and melt-freeze crusts are found, which seems to be still reactive in isolated areas.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-160 cm. This layer was reactive early last week producing large size 3 avalanches.

Activity has tapered, however, daytime warming, sun, cornice fall, and human triggers from steep, rocky slopes, with a shallow or thin-to-thick snowpack may still be able to trigger this weak layer. 

• In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
• Start on smaller terrain features and gather information before committing to bigger terrain.
• Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
• Avoid terrain traps where the consequence of any avalanche could be serious.