Avalanche Forecast
Issued: Jan 1st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs, Deep Persistent Slabs and Persistent Slabs.
zryan,
Avalanche Canada
A tricky-moderate danger rating is a result of a shallow, weak, and atypical coastal snowpack.
Avoid wind-loaded areas at upper elevations. Recently formed wind slabs overlie a slick crust in some areas and could remain reactive to human triggering for longer than is typical. Concern for buried weak layers in the mid to lower snowpack should have you sticking to conservative, low-consequence terrain.
Summary
Confidence
Moderate
Avalanche Summary
Last Wednesday, a large size 3 avalanche was remotely triggered by skiers roughly 100 m away. The avalanche was on a northeast aspect at 2050 m. It ran on a weak layer of surface hoar (80 to 100 cm deep), before scrubbing down to the ground in steep terrain.
Observations remain limited, and no reports of new avalanches have been made since Wednesday.
Please continue to post your observations and photos to the Mountain Information Network.
Snowpack Summary
This week, 10-25 cm of storm snow was accompanied by strong southwest winds, creating hard wind-affected surfaces in open areas, and wind slabs in lee terrain features. This new snow overlies a rain crust formed earlier in the week. This crust is thin at higher elevations and up to 5 cm thick below treeline.
In the mid-snowpack, a weak layer of surface hoar has been observed down 80-100 cm, this layer is most prevalent in shaded and sheltered areas.
The lower snowpack consists of weak, sugary crystals of facets and depth hoar.
Snowpack depths remain highly variable, roughly 50 to 200 cm at treeline.
Weather Summary
Sunday night
Clear periods. Alpine temperatures drop to a low of -9 °C. Ridge wind light to 20 km/h from the south. Freezing level at valley bottom.
Monday
Sunny with cloudy periods. Alpine temperatures reach a high of -1 °C. Ridge wind light to 25 km/h from the southwest Freezing level rises to 1600 metres.
TuesdayA mix of sun and cloud. Alpine temperatures reach a high of -5 °C. Mostly light ridge wind occasionally gusting to 35 km/h from the southwest. Freezing level at valley bottom.
WednesdayA mix of sun and cloud. Alpine temperatures reach a high of -5 °C. Mostly light ridge wind occasionally gusting to 35 km/h from the southwest. Freezing level at valley bottom.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Be mindful that deep instabilities are still present and have produced recent large avalanches.
- Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
Problems
Wind Slabs
During last week's storm, strong southerly winds redistributed 15 - 20 cm of new snow into deep deposits of wind slabs at higher elevations. These wind slabs may remain reactive to human triggering, particularly where they overlie a slick crust.
Keep in mind that wind slab avalanches have the potential to step down to deeper weak layers creating large avalanches.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The winter snowpack is not as deep as usual, and along with a cold and dry early winter, the lower snowpack consists of weak, unconsolidated facets and depth hoar crystals. With weak basal layers, a cautious approach to large open terrain features is required especially around rocky or thin areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar has been reported down 80 - 100 cm. This layer is of greatest concern on shaded, northerly aspects and in thinner snowpack areas where human-triggering is most likely.
Remote triggering is a concern for this layer (triggering from an adjacent slope or from below). If triggered, this layer has the potential to step down to the weak faceted lower snowpack, creating large and destructive avalanches.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 2nd, 2023 4:00PM
