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 and Deep Persistent Slabs.
zryan,
Avalanche Canada
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.
A low-probability but high-consequence deep persistent slab problem should have you avoiding thin rocky areas and exposure to overhead hazards. Learn more about how to manage this problem in the avalanche summary...
Summary
Confidence
Moderate
Avalanche Summary
On Friday and Saturday, numerous natural and human-triggered storm and wind slabs were reported up to size 2. These slabs mainly occurred in wind-loaded terrain and primarily failed on the underlying rain crust.
Several large (size 2 to 2.5) deep persistent slab avalanches were produced during explosive control work last Thursday. All in alpine terrain on a variety of aspects with crowns of 1.5 to 2 m deep. This layer now presents a low-probability but high-consequence problem that is atypical for our coastal snowpack. Learn more about the nature of this deep persistent slab problem from this forecaster blog.
Looking forward, wind slabs may remain reactive to human triggering for longer than is typical due to the slick crust they are sitting on. Avoid wind-loaded terrain and watch for signs of instability as you travel.
Please continue to post your observations and photos to the Mountain Information Network.
Snowpack Summary
Last week, 30-60 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 and breakable at higher elevations and up 10 cm thick at lower elevations.
The mid-snowpack consists of moist snow below a crust at lower elevations and a series of crusts and denser snow at upper elevations.
Near the base of the snowpack, a weak facet/crust layer can be found.
Total snow depths are roughly 100 to 200 cm at treeline.
Weather Summary
Sunday night
Mainly cloudy. Alpine temperatures drop to a low of -5 °C. Ridge wind south 15-25 km/h. Freezing level at valley bottom.
Monday
Cloudy with sunny periods. Alpine temperatures reach a high of -1 °C. Ridge wind south 15 km/h gusting to 40 km/h. Freezing level rises to 1400 metres.
TuesdayCloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -5 °C. Ridge wind southwest 10-25 km/h. Freezing level rises to 800 metres.
WednesdayCloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -2 °C. Ridge wind southeast 15-30 km/h. Freezing level rises to 1200 metres.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Keep in mind the crust offers an excellent bed surface for avalanches.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
Problems
Wind Slabs
Last week's snowfall was accompanied by strong southwesterly winds, creating deep deposits of wind slab in lee terrain features. Wind slabs may remain reactive to human triggering for longer than is typical as they overlie a slick rain crust formed early last week.
Keep in mind that if triggered, wind slabs may step down to deeper layers resulting in very large avalanches.
Aspects: North, North East, East, South East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
A crust with weak, faceted snow above and below exists near the base of the snowpack. Human-triggering this layer is unlikely, but large loads such as cornice fall or a smaller avalanche stepping down to this layer are possible. Avoid thin, rocky, wind-affected areas were triggering this layer is most likely.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 2nd, 2023 4:00PM
