Avalanche Forecast
Issued: Jan 25th, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs, Wind Slabs and Persistent Slabs.
rgoddard,
Avalanche Canada
Large natural and human-triggered avalanches have occurred in our region over the past couple of days.
The complex and weak snowpack is not going away anytime soon.
Conservative terrain choices should continue to be your game plan.
Summary
Confidence
Moderate
Avalanche Summary
On Tuesday there was a report of a size 3.5 natural avalanche in the Dogtooth Range. This was likely a deep persistent avalanche with a wide propagation triggering near ridgetop at the upper end of treeline on an easterly aspect.
On Monday there was a size 3 skier triggered deep persistent avalanche on an east aspect starting at 2300m in the Terminator area in the Dogtooth Range. This MIN outlines the avalanche.
There was an avalanche of note on Saturday. It was a size 2 that a skier triggered accidentally. This avalanche was of note because it was from our persistent slab problem, buried surface hoar and because it happened on such a low angle. Our persistent slab problem and deep persistent slab problem are still problems.
Snowpack Summary
Surface hoar can be found to be developing on the snow surface at most elevations and aspects in the western and northern parts of our region. Sun is beginning to have an effect on steep solar slopes. Wind slabs can be found in exposed areas at higher elevations.
The mid-snowpack contains a couple of layers of major concern. The first is down 30 to 50 cm and is a layer of surface hoar from early January. The second is a layer of surface hoar, facets, and crust created in December and found 40 to 90 cm down. The surface hoar is most prevalent in sheltered areas while crusts and any associated faceted snow are more widespread.
The bottom of the snowpack is weak and faceted. The total depth of this weak and shallow snowpack ranges between 80 and 180 cm at treeline and is shallowest in the eastern part of our region.
Weather Summary
Wednesday Night
Increasing clouds, possible trace accumulation, wind west 25 to 30 km/h gusting to 50, treeline temperatures -3 C.
Thursday
Cloudy with sunny breaks, trace accumulation, wind west 20 km/h gusting to 50, treeline temperatures at -2 C with freezing level climbing to 1000 m.
Friday
Mainly cloudy, 6 to 12 cm accumulation, wind northwest 20 km/h, treeline temperatures -5 to -8 C.
Saturday
A mix of sun and cloud, trace accumulation early in the morning, wind north 15 km/h, treeline temperatures -18 C.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
- Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
- Uncertainty is best managed through conservative terrain choices at this time.
- Avoid areas with overhead hazard.
- Be carefull around freshly wind loaded features.
- Choose slopes that are well supported and have limited consequence.
Problems
Deep Persistent Slabs
A weak layer near the base of the snowpack, buried in November, has been recently reactive in the Dogtooth Range . Human and natural triggering of this layer remains possible, especially in shallow areas with variable snow depths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Wind Slabs
Westerly winds are expected to have created slabs in exposed areas at higher elevations.
Aspects: North, North East, East, South East, South, North West.
Elevations: Alpine.
Likelihood
Expected Size
Persistent Slabs
The top metre of the snowpack holds a couple of weak layers which are at depths that can be triggered by human activity. Down 20 to 40 cm from the surface there is a surface hoar layer that was buried in early January. Below this, down 40 to 70 cm from the surface there is a layer made of surface hoar, facets and or a crust that us from December.
Smaller avalanches could create a "domino effect" and create large avalanches that encompass massive areas.
Aspects: All aspects.
Elevations: All elevations.
Likelihood
Expected Size
Valid until: Jan 26th, 2023 4:00PM
