Avalanche Forecast

Wednesday night: Flurries and snow, 15-25 cm. Alpine low temperature -9 C. Moderate southwest winds gusting to extreme.

Thursday: Snow, heavy in some areas, 20-40 cm. Alpine high temperature -3 C. Strong gusting to extreme southwest winds. Freezing level rising to 1000 m.

Friday: Flurries and snow, 10-20 cm. Alpine high temperature -3 C. Moderate southwest winds gusting strong to extreme. Freezing level 700 m.

Saturday: Flurries and snow, 5-15 cm. Alpine high temperature -7 C. Moderate southwest wind gusting to strong. Freezing level dropping to valley bottom.

Small (size 1-1.5) storm slabs were triggered by explosives further north in the region on Wednesday. A few larger (up to size 2.5) slab avalanches failed naturally overnight, likely due to a combination of new snow and strong wind. As more snow accumulates with strong winds, storm slabs are expected to grow in size and reactivity.

Last Sunday, small pockets of human-triggered wind slab were recently reported at treeline elevations closer to Terrace, while larger (size 2-3.5) wind slabs were reported further north in the Bear Pass area releasing naturally from alpine start zones. Several of these avalanches released down to a weak layer formed in mid-January. During the weekend warm-up, numerous natural loose wet avalanches in steep terrain (size 1-2) were observed up to 1000 m. 

Reports of deep persistent slab avalanches have been trickling in throughout the month, with a size 2.5 deep persistent avalanche triggered by explosives in the Ningunsaw area on Tuesday. Prior to this avalanche, the last reported event occurred on Jan 17th. They are associated with a November crust layer near the base of the snowpack which has produced very large avalanches (size 3+) with crown depths of around 2 m. These have typically run in alpine terrain, on lee or cross-loaded slopes. Recent loading has been a good test for this layer and it seems to be trending less reactive.

A powerful storm is impacting the region with intense snowfall and extreme winds. Rapid snow accumulations are expected to build a touchy storm slab problem, particularly in wind-exposed areas. The intensity of the wind has the potential to reach areas well below treeline and form slabs in normally sheltered areas. Freezing levels are forecast to rise during the storm to 1000 m.

Last week's 50-120 cm of snow accumulation rests on a mix of previously scoured surfaces from the arctic outflow winds or a thick layer of weak facets. Recent avalanche activity in the Bear Pass area and snowpack tests results have indicated that this layer is still a concern (check out this MIN report). Below tree line, a recent warm-up moistened snow surfaces up to 900 m, forming a temperature crust. 

A crust from mid November lurks at the base of the snowpack. The last reported avalanche on this layer was Jan 17th. While it is promising that last week's significant snowfall did not trigger avalanches on this deep persistent weak layer, there is lingering uncertainty as to whether this week's weather could meet the threshold. 

• Use increased caution at all elevations. Storm snow is forming touchy slabs.
• Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
• Be aware of the potential for human triggerable storm slabs at lower elevations, even on small features.
• Storm slabs in motion may step down to deeper layers resulting in large avalanches.