Avalanche Forecast
Issued: Dec 11th, 2022 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Storm Slabs.
rgoddard,
Avalanche Canada
7:30 AM Update: Large skier-triggered avalanches have occurred in our region in the last few days!
Storm slabs and buried weak layers can surprise and create large avalanches.
Assess conditions while you travel and choose your terrain carefully. Watch and feel for signs of instability such as whumpfing, cracking, and recent avalanches.
Summary
Confidence
Moderate
Avalanche Summary
A group of skiers reported triggering a large avalanche, size 2, that released on the mid-November weak layer. Similar activity occurred on Sunday near Hosmer. This layer is still around and can be expected to produce avalanches if triggered in the "right" spot or by a heavier load.
Late in the day Sunday there was a report of a large size 3, skier-triggered avalanche in the Lizard Range. Three people were involved, with one fully buried. They were dug out by their companions. Details are not yet known at this time but more information will follow.
Thank you all for supporting your community and reporting in the MIN.
Snowpack Summary
Up to 30 cm of snow has fallen since Thursday. This sits on a variety of surfaces. In the alpine and at treeline, it sits mostly on wind slabs that were created by southwesterly winds that we experienced earlier this past week.
Below the 30 cm of new snow sits about 20 to 30 cm of more consolidated snow. Just below this is where our mid-November weak layer, consisting of facets and surface hoar. A widespread rain crust remains near the ground, at the treeline, and below the treeline.
At treeline, snowpack depths vary from 120 to 200 cm.
Weather Summary
Sunday Night
Mostly cloudy, up to 5 cm accumulation, winds northeast 10 gusting to 30 km/h, temperature -10 C at 1500 m.
Monday
A mix of sun and cloud, trace accumulation, winds northeast 10 gusting to 30 km/h, temperature -10 C at 1500 m.
Tuesday
Cloud in the morning with more sun in the afternoon, no accumulation, winds northwest 10 to 20 km/h, temperature -9 C at 1500 m.
Wednesday
Cloudy with sunny periods, 2 cm accumulation, winds west 10 km/h, temperature -10 C at 1500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Back off if you encounter whumpfing, hollow sounds, or shooting cracks.
- In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
- Be especially cautious as you transition into wind affected terrain.
- Fresh snow rests on a problematic persistent slab, don't let good riding lure you into complacency.
- If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
Problems
Persistent Slabs
Buried layers of surface hoar and facets have been reactive to human triggers in recent days. Reactivity has been observed in sheltered areas at treeline, where the surface hoar may be preserved, and in wind-loaded areas at upper elevations, where a cohesive slab has been formed above.
Recent warmer temperatures could have consolidated the top layer of fresh snow into a slab.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Storm Slabs
New snow with little wind is accumulating on a variety of surfaces that include a layer of low-density lighter snow. Warmer temperatures are expected to consolidate this new snow into a slab.
Small avalanches in the upper snowpack could trigger deeper weak layers, creating a larger-than-expected avalanche.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Dec 12th, 2022 4:00PM
