Avalanche Forecast

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

A ridge of high pressure continues to bring clear skies and dry conditions into Saturday. 

Friday Overnight: Clear. Freezing level dropping to valley bottom. Light ridgetop winds. 

Saturday: Mainly clear, some valley cloud may develop. Freezing level rising to 1300 m with an alpine temperature inversion. Light northwest winds at ridgetop.

Sunday: Cloud cover increasing. Freezing level rising to 1000m. Light westerly winds at ridgetop.

Monday: Snowing. Freezing level rising to 1000 m in the afternoon. Light to moderate westerly winds at ridgetop.

On Friday, several natural wind slabs were observed in east-facing lee features in the alpine.

A persistent weak layer of buried surface hoar continues to be reactive to human triggered producing numerous large avalanches in the past week, surprising both professionals and recreationists. This layer has shown the most reactivity between 1600-2200 m in open areas in the trees, in cut blocks and on steep convexities. Compelling observations on this layer from the neighbouring region of Glacier National Park can be seen here. 

Overnight, clear skies and cooling temperatures will refreeze the surface of the snowpack. A thin breakable crust exists on most aspects and elevations, while a thicker more prominent crust can be expected at lower elevations and on south-facing aspects. Warm daytime temperatures and strong solar radiation will likely cause these crusts to break down throughout the day.

Strong westerly winds in the past week have created extensive wind-effect in open areas at all elevations. Expect to find old and new wind slabs on a variety of aspects, with the most recent and reactive slabs formed in terrain features lee to the northwest. 

Several weak layers exist in the upper snowpack including buried crusts, facets, and a prominent weak layer of surface hoar. This surface hoar is the dominating feature. It was buried in late January and exists 60 to 100 cm deep in the snowpack. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline.

The facet/crust layer that formed in early December is buried around 120 to 250 cm. The last reported avalanche was on January 31 from a large explosive, and before that on January 23. Although unlikely, the layer could be triggered from a large load like a cornice fall or a shallower slab avalanche could step down to this layer. Humans are unlikely to trigger it, with perhaps the exception in thin, shallow snowpack areas. Check out the forecaster blog for more information.

• Uncertainty is best managed through conservative terrain choices at this time.
• Be aware of the potential for large avalanches due to the presence of buried surface hoar.
• Surface hoar distribution is highly variable. Avoid generalizing your observations.
• If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
• Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.