Avalanche Forecast
Issued: Jan 7th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
JSmith,
Avalanche Canada
Forecast strong southerly winds will continue to form fresh wind slabs on lee features at treeline and above. Avoid freshly wind loaded features, especially near ridge crests, roll-overs, and in steep terrain.
Summary
Confidence
Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.
Weather Forecast
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THURSDAY NIGHT: Partly cloudy / Moderate, southeast ridgetop wind / alpine low temperature -10 / Freezing level valley bottom.
FRIDAY: Mostly cloudy / Strong, southwest ridgetop wind / alpine high temperature -6 / Freezing level valley bottom.
SATURDAY: Mix of sun and cloud / Light, southwest ridgetop wind / alpine high temperature -8 / Freezing level valley bottom.
SUNDAY: Cloudy with isolated flurries; 0-3 cm. / Moderate, southwest ridgetop wind / alpine high temperature -5 / Freezing level valley bottom.
Avalanche Summary
Since New Year's there have been steady reports of natural wind slab avalanches in alpine terrain (size 1-2), and some smaller human-triggered wind slab avalanches in lee terrain (size 1). There are good photos of these avalanches in recent MIN reports (e.g. here, here, here, and here). While there have been no reports of persistent slab avalanches since Dec 22, there have been reports of large whumpfs in the Hudson Bay, Hankin, and Babines area over the past few days, suggesting the buried weak layers are still possible to trigger.
Snowpack Summary
Strong wind is moving around 40-60 cm of snow that has fallen since New Year's Day. Reactive wind slabs can be found in exposed open terrain, while lower density snow can be found in sheltered terrain. In some parts of the region this snow could be sitting above a surface hoar layer and forming isolated storm slabs on steep rolls in sheltered areas.
The lower snowpack has two crusts with potentially weak snow around them. Reports from the Smithers area suggest the upper crust is 60-90 cm below the surface and has shown signs of being possible to trigger from shallow areas. The other crust is near the bottom of the snowpack, and may be possible to trigger from shallow rocky slopes.
Terrain and Travel
- Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
- Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
- Be especially cautious near rock outcroppings, on steep convexities and anywhere the snowpack feels thinner than average.
- Be aware of the potential for large avalanches due to the presence of a persistent slab.
Problems
Wind Slabs
Intense wind from the south has left touchy slabs in leeward terrain. Most of the wind loading should be on northeast slopes, but shifting winds over the past few days may have left unstable slabs on all aspects. In some isolated sheltered areas recent snow may be settling above surface hoar.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
Triggering large avalanches on weaknesses in the lower snowpack remains a possibility. In some areas the concern is weak snow around crusts 60 to 90 cm deep, while in others it is weak snow near the bottom of the snowpack. This problem is best managed by avoiding steep rocky slopes and approaching challenging and complex avalanche terrain with extra caution.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 8th, 2021 4:00PM
