Avalanche Forecast

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

The ridge of high pressure will start to break down with increasing cloud cover and the potential for light precipitation.

Saturday Overnight: Mainly clear, some valley cloud may develop. Freezing level dropping to near valley bottom. Light southwest winds at ridgetop.

Sunday: Mainly cloudy with light precipitation. Freezing level rising to around 1500 m in the afternoon. Light southwest winds at ridgetop.

Monday: Cloudy with snowfall. Freezing level around 1000 m. Light to moderate southwest winds at ridgetop.

Tuesday: Mainly cloudy with light snowfall. Freezing level 500 to 1000 m. Moderate to strong southwest winds at ridgetop. 

On Friday, sledders near Blue River remote triggered several large slab avalanches on shaded aspects at treeline. The failure plane of these avalanches is uncertain, but large remote triggered avalanches would make us suspect it failed on the late January buried surface hoar. Photos from this incident can be seen here.

Operators observed several natural and human-triggered wind slabs on Thursday in lee areas in the alpine as strong northwesterly winds redistributed available snow. One notable persistent slab result in the south of the region occurred in a wind-loaded feature in the alpine on the January 30th surface hoar layer.

As a result of the rain event last Wednesday, operators in the north of the region observed a large natural avalanche that initiated as a storm slab in the alpine and gouged to ground lower down in the track in wet, uncohesive snow.

Overnight, warmer temperatures and cloud cover may promote a weaker refreeze on the surface of the snowpack. A thin breakable crust exists on almost all aspects and elevations, while a thicker more prominent crust can be expected at lower elevations and on south-facing aspects. Warm daytime temperatures and the potential for light rain at lower elevations may cause these crusts to break down throughout the day.

In the north of the region, a rain event earlier in the week created a widespread curst on the snow surface of variable thickness that extends all the way to mountain top. Where this crust is thick and supportive, avalanches are unlikely. 

Strong westerly winds throughout the week have created extensive wind-effect in open areas in the alpine and treeline. Expect to find old wind slabs on a variety of aspects, that will likely be unreactive to human triggering after several days of warm temperatures.

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. Terrain features to be suspect of includes the lee side of protected ridges, openings in the trees, cut blocks, and burns. 

The lower snowpack is generally strong and well-bonded.

• When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.
• Be aware of the potential for large avalanches due to the presence of buried surface hoar.
• As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.