Avalanche Forecast
Regions: Sea To Sky.
The outflow winds are forecast to peak on Tuesday. Due to the recently shifting wind directions, thin new wind slabs should be expected on all aspects in exposed terrain.
Confidence
Moderate - Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.
Weather Forecast
Arctic high pressure brings a couple more days of cold conditions before returning to seasonal temperatures by Thursday.Â
Monday Night: Clear, moderate to strong NE wind, treeline low around -20 °C.
Tuesday: Sunny, moderate to strong NE wind, treeline high around -12 °C.
Wednesday: Mainly sunny with some cloud in the late afternoon, wind becoming moderate NW in the afternoon, treeline high around -8 °C.
Thursday: Sunny, light to moderate N wind, treeline high around -4 °C.
Avalanche Summary
On Sunday, natural size 1 wind slabs were being observed as well as some isolated natural loose activity. A natural size 2 cornice was also reported which did not trigger a slab.Â
On Thursday, a natural icefall triggered a size 2.5 slab avalanche on the slope below. This avalanche was on a northeast aspect at 2100Â m. Details were limited but we expect this may have been a persistent slab avalanche.Â
Snowpack Summary
The weekend storm produced 5-10 cm of snow with strong southwest wind that likely formed thin wind slabs in exposed terrain. On Monday, the wind switched to a northeast direction causing reverse loading and thin wind slabs should now be expected on all aspects.Â
The mid-February crust is down 10-30Â cm. This melt-freeze crust is reported to exist on all aspects and elevations, except for some of the highest elevation polar aspects. Facets have been observed above the crust on polar aspects.
The late-January crust/facet/surface hoar interface is buried down 40-100Â cm. This layer was most reactive between 1700 m and 2000 m. While this layer now appears to be dormant through most of the region, it may still be possible to trigger it at upper treeline or lower alpine features on polar aspects with a large load like a cornice or in shallow snowpack areas.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Recent wind has varied in direction so watch for wind slabs on all aspects.
- Closely monitor how the new snow is bonding to the crust.
- Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.
Avalanche Problems
Wind Slabs
5-10 cm of snow fell over the weekend accompanied by southwest wind. On Monday, the wind switched to the northeast and has likely caused reverse loading. Thin wind slabs should now be expected on all aspects in exposed terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 2
Persistent Slabs
The late-January weak layer is down 40-100 cm and was most reactive between 1700 and 2000 m. It is now likely dormant in many areas. It is likely only possible to trigger on polar aspects at upper treeline or lower alpine where the mid-February crust is thinner and not bridging.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 2 - 3