Avalanche Forecast
Issued: Feb 15th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
swerner,
Avalanche Canada
New snow will bond poorly to the underlying crust. Small but reactive pockets of wind slab may form in lee areas in the alpine and treeline.
Manage open slopes at treeline carefully where triggering a persistent slab avalanche is most likely.
Summary
Confidence
High -
Weather Forecast
A passing frontal system will bring light snowfall, with greater amounts forecast for Thursday.
Tuesday Overnight: Mainly cloudy, light snowfall 5 cm. Freezing level dropping to valley bottom. Light to moderate northwesterly winds.Â
Wednesday: Partially cloudy with light flurries. Freezing level rising to 1000 m. Moderate northwesterly winds.Â
Thursday: Mainly cloudy and snowing with 5-10 cm forecast. Freezing level rising to 1500 m in the afternoon. Moderate to strong northwesterly winds.Â
Friday: Snowing, heavy at times 10-20 cm. Freezing level rising to 1500m. Strong to extreme westerly winds.Â
Avalanche Summary
If you see more than 10 cm of fresh snow expect to see some isolated pockets of reactive wind slab on leeward slopes and terrain features on Wednesday.
On Monday, a natural cornice fall size 1.5 was reported and did not pull a slab from the slope below. The aspect and elevation are unknown.Â
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 (a week ago), 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
- Wind slabs may be poorly bonded to the underlying crust.
- 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
Wind Slabs
New snow may be redistributed by northwest winds to create small but reactive pockets of wind slab in the alpine and treeline.
Aspects: North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer formed 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 16th, 2022 4:00PM
