Avalanche Forecast
Issued: Feb 13th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs.
zryan,
Avalanche Canada
Danger remains elevated at treeline with an ongoing concern for persistent slab avalanches. Use extra caution in shaded and sheltered areas where triggering persistent slab avalanches is most likely.
Avalanches are unlikely in areas where a hard surface crust is present.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
A passing frontal system will bring a more unsettled weather pattern with light snowfall expected throughout the week.
Sunday Overnight: Cloudy with the potential for light snowfall. Light southerly winds at ridgetop. Freezing level around 500 m.
Monday: Cloudy with light snowfall. Light westerly winds at ridgetop. Freezing level around 1000 m.
Tuesday: Cloudy with light snowfall. Light to moderate northwest winds at ridgetop. Freezing level around 500 m.
Wednesday: Cloudy with light snowfall. Light to moderate northwest winds at ridgetop. Freezing level rising to 1300m in the afternoon.
Avalanche Summary
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.
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.
Snowpack Summary
New snow is expected to bond poorly to the old surface. This surface is comprised of near-surface faceting and in some areas, surface hoar growth overlying a melt-freeze crust at lower elevations, a sun-crust on steep solar aspects, and hard wind-affected snow in the alpine and exposed treeline.Â
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.Â
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.Â
The lower snowpack is generally strong and well-bonded.
Terrain and Travel
- 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.
- Surface hoar distribution is highly variable. Avoid generalizing your observations.
Problems
Persistent Slabs
A weak layer formed by clear skies in late January may be found 50 to 100 cm deep in the snowpack. This layer consists of facetted snow, a sun crust on steep solar aspect, and most notably large surface hoar crystals in sheltered terrain.
This layer has been the culprit of several large human-triggered avalanches in the past week and remains a concern, especially in sheltered areas at treeline and below. Terrain features to be particularly cautious around include the lee side of ridges, openings in trees, cut blocks, and burns. Triggering this layer from a distance away is a concern, watch out for adjacent and overhead slopes.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 14th, 2022 4:00PM
