Avalanche Forecast
Issued: Feb 11th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs, Wind Slabs and Loose Wet.
zryan,
Avalanche Canada
A dangerous dilemma exists in sheltered, shaded areas where dry powder may be preserved, but a lethal layer of surface hoar could remain ripe for human triggering.
These beautiful warm sunny days are best enjoyed in low angled alpine terrain with no exposure to overhead hazard.
Summary
Confidence
Weather Forecast
A ridge of high pressure continues to bring mainly clear skies and dry conditions into Saturday.
Friday Overnight: Mainly clear. Freezing level dropping to valley bottom. Moderate to strong northwest winds at ridgetop.
Saturday: Mainly clear, some valley cloud may develop. Freezing level rising to 1300 m with an alpine temperature inversion. Light to moderate northwest winds at ridgetop.
Sunday: Cloud cover increasing. Freezing level rising to 1000m. Light to moderate westerly winds at ridgetop.
Monday: Snowing. Freezing level rising to 1000 m in the afternoon. Light to moderate westerly winds at ridgetop.
Avalanche Summary
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 on Wednesday, operators 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.
Throughout the week, sporadic reports of human-triggered avalanches on the January 30th weak layer have indicated that this layer remains problematic and has the potential to surprise riders with large, consequential avalanches.
Snowpack Summary
Overnight, clear skies and cooling temperatures will refreeze 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 strong solar radiation will likely cause these crusts to break down throughout the day.
Strong westerly winds throughout the 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. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns.
The lower snowpack is generally strong and well-bonded.
Terrain and Travel
- 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 steep slopes when air temperatures are warm, or solar radiation is strong.
Problems
Persistent Slabs
A weak layer formed by clear skies and warm temperatures 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 as the snowpack is being tested with warm temperatures and strong solar radiation.
The problematic surface hoar layer will be most prominent 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
Wind Slabs
Strong westerly winds throughout the week have created wind slabs in the alpine. Wind slabs may be stubborn to human triggering but have the potential to step down to buried weak layers, creating large avalanches.
Cornices may become weak with warm temperatures. Cornice failures put a large load on the snowpack, and have the potential to trigger buried weak layers, resulting in large destructive avalanches.
Aspects: North, North East, East, South East, South.
Elevations: Alpine.
Likelihood
Expected Size
Loose Wet
Warm temperatures compounded by strong solar radiation may create wet loose avalanches on steep solar aspects in the afternoon.
Aspects: South East, South, South West, West.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Feb 12th, 2022 4:00PM
