Avalanche Forecast
Issued: Feb 14th, 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
Manage open slopes at treeline carefully where triggering a persistent slab avalanche 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 more unsettled weather pattern will bring a mix of sun and cloud and light snowfall throughout the week.
Monday Overnight: Cloudy with snowfall in most areas. Freezing level dropping to valley bottom. Light to moderate northwesterly winds.
Tuesday: A mix of sun and cloud, light flurries. Freezing level rising to 1000 m. Light to moderate northwesterly winds.Â
Wednesday: A mix of sun and cloud, light flurries. Freezing level rising to 1000 m. Light to moderate northwesterly winds.Â
Thursday: Snowing. Freezing level rising to 1500m. Moderate to strong westerly winds.Â
Avalanche Summary
Last 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
A light amount of 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
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 40 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 40 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 of surface hoar 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. Where a thick, supportive crust is present on the surface, avalanches on this layer are unlikely. 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 15th, 2022 4:00PM
