Avalanche Forecast
Issued: Jan 9th, 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.
ahanna,
Avalanche Canada
Watch for wind slabs that may remain sensitive to human triggers and keep in mind the lingering potential for large and destructive persistent slab avalanches.
Summary
Confidence
Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.
Weather Forecast
Saturday night: Increasing cloud, light to moderate southeast wind, freezing level valley bottom.
Sunday: Flurries, trace, moderate southeast wind, alpine high -8, freezing level 700 m.
Monday: Flurries, 5-10 cm, moderate southwest wind, alpine high -6, freezing level 1200 m.
Tuesday: Snow, 10-20 cm, strong southwest wind, alpine high -6, freezing level 1200 m.
Avalanche Summary
We have received few reports of avalanche activity in the region since the mid-week storm slab avalanche cycle produced natural avalanches size 2-3.5. But with similar snowpack structure and recent weather patterns to neighboring Glacier National Park and South Columbia regions, we suspect that recent avalanche activity has been similar, but has gone unreported due to less backcountry traffic.Â
Natural storm slab avalanches size 1.5-2.5 have been reported in GNP as recently as Friday. Notable avalanches in South Columbia include several skier triggered incidents around size 2 in the RMR slackcountry and a few natural persistent slab avalanches size 2.5-3 on northerly aspects in the alpine running on the early December persistent weak layer. See South Columbia avalanche summary for details.
Snowpack Summary
Variably wind affected surfaces can be found at upper elevations. Around 50-80 cm of recent snow sits on a weak layer of surface hoar that was buried around Christmas at and below treeline.
A couple of persistent weak layers buried in early/mid-December are buried 90-150 cm down. Generally, they can be found as a layer of surface hoar above in close proximity to a crust/surface hoar layer. The form and distribution of these layers are highly variable and conditions may differ significantly from one valley to the next.Â
Terrain and Travel
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Previous snow and wind have created deep pockets of wind slab in lee terrain features at upper elevations. These were very reactive before the weekend and may remain sensitive to human triggers.
Cornices have also been growing. A cornice fall is a large load that can trigger avalanches on the slope below.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar that was buried around Christmas is now down about 50-80 cm and is most prevalent at treeline and below treeline.
Two more persistent weak layers buried in early/mid-December are now 90-150 cm below the surface. The form and distribution of these layers are highly variable and may vary significantly from one valley to the next, and between elevation bands.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 10th, 2021 4:00PM
