Avalanche Forecast
Issued: Feb 7th, 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.
ldreier,
Avalanche Canada
Human triggered avalanches that release on the buried weak layer keep surprising skiers and riders. The uncertainty on where and if this layer can be triggered is best managed with conservative terrain choices.
Summary
Confidence
Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
MONDAY NIGHT: Clear with cloudy periods, up to 3 cm new snow, light to moderate west wind, alpine temperature -4 C, freezing level 600 m.
TUESDAY: Cloudy, up to 5 cm new snow, light southwest wind, alpine temperature -2 C, freezing level 1400 m.Â
WEDNESDAY: Cloudy, 10 to 15 cm new snow, light southwest wind, alpine temperature 0 C, freezing level rising to 2100 m.Â
THURSDAY: Sunny with cloudy periods, up to 3 cm new snow, light to moderate southwest wind, alpine temperature +2 C, freezing level 2500 m.
Avalanche Summary
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.
On Saturday, several storm and wind slab avalanches up to size 2.5 were observed at treeline and in the alpine. Most released naturally, and a couple were likely triggered by riders. Skiers triggered a large avalanche remotely in the south of the region (see this MIN report for details - thank you for the report).
Observations on Friday were limited due to bad visibility. A natural avalanche cycle of small storm slab avalanches up to size 1.5 was reported.
Snowpack Summary
The recent storm brought around 30 to 50 cm of snow. The snow formed wind slabs in lee terrain features from strong southwest wind and storm slabs in wind sheltered areas.
The snow will be particularly touchy where it loaded a weak layer of surface hoar crystals. This layer is likely anywhere from 50 to 100 cm deep. 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
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- 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
The recent snow loaded a widespread weak layer of surface hoar crystals. The layer 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.
The buried weak layer was reported to be very active in the Wells Gray area and Blue River area at all elevations and is present up to treeline at Mica Mountain and around Valemount.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Wind Slabs
Strong southwest wind has formed wind slabs in lee terrain features at higher elevations. Wind slabs are especially touchy where they overlie a buried weak layer with surface hoar crystals.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Feb 8th, 2022 4:00PM
