Avalanche Forecast
Issued: Feb 10th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Wind Slabs.
zryan,
Avalanche Canada
Uncertainty remains around a buried weak layer in the upper snowpack.
This is a good time to make conservative terrain choices, particularly when warm temperatures and solar radiation are testing the snowpack.
Summary
Confidence
Low - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
A building ridge of high pressure will usher in clear skies and warm temperatures.Â
Thursday overnight: Clearing. Ridge winds 40-70 km/h from the northwest. Freezing level dropping to valley bottom.
Friday: Mainly clear. Ridge winds 20-60 km/h from the west. Freezing level rising to 1000 m in the afternoon.
Saturday: Mainly clear. Ridge winds 20-50 km/h from the west. Freezing level rising to 1600 m in the afternoon.
Sunday: Mainly cloudy. Ridge winds light from the west. Trace precipitation. Freezing level rising to 1800 m.
Avalanche Summary
On Tuesday, skiers triggered small slabs on the buried weak layer with surface hoar. One was triggered from a distance away.
On Monday, wet loose avalanches below 1000 m were observed. Observations were limited due to visibility.
On Sunday, two natural large avalanches of size 2-2.5 were observed in steep terrain on north and east aspects in the alpine. Several large avalanches released on sun exposed steep slopes. Riders triggered a large size 3 avalanche in the south of the region.
Snowpack Summary
Overnight, clear skies and cooling temperatures will refreeze the surface of the snowpack at lower elevations where it has been affected by rain and warm temperatures. Strong northwest winds have created extensive wind-effect 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.Â
A weak layer of surface hoar exists 60 to 100 cm deep in the snowpack, which is a prime depth for human triggering. Reports suggest that the surface hoar is most prominent in sheltered openings at and below treeline but could extend into wind-sheltered terrain in the alpine. Example terrain features to treat as suspect include the lee side of protected ridges, openings in the trees, cut blocks, and burns. On south aspects, a melt-freeze crust may exist instead of surface hoar.
The lower snowpack is generally strong and well-bonded.
Terrain and Travel
- Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
- Be aware of the potential for large avalanches due to the presence of buried surface hoar.
- Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
- Uncertainty is best managed through conservative terrain choices at this time.
Problems
Persistent Slabs
A layer of buried surface hoar may be found around 50 to 100 cm deep and is most prominent in areas sheltered from the wind at and below treeline. Example terrain features to particularly treat as suspect 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.
The buried weak layer was reported to be active in the Blue River area at all elevations and in the Wells Gray area below treeline. And it is present up to treeline at Mica Mountain and around Valemount.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Strong westerly winds throughout the week have created a smorgasbord of wind slabs in the alpine and exposed treeline. Wind slabs may be stubborn to human triggering but have the potential to step down to buried weak layers, creating large avalanches.
Aspects: North, North East, East, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 11th, 2022 4:00PM
