Avalanche Forecast
Issued: Mar 19th, 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.
rgoddard,
Avalanche Canada
Use caution when transitioning into wind-affected terrain.
Stick to thick snowpack areas where you are less likely to trigger deep weak layers.
Summary
Confidence
High
Avalanche Summary
On Friday afternoon, a snowmobile triggered a large persistent slab avalanche (size 2.5) in the south Purcells. The avalanche occurred in burnt forested terrain on a south aspect at 2200 m. It failed on a 50 to 100 cm deep layer that is suspected to be a sun crust buried in February.
On Thursday in the Elk Valley, several size 3 wind slab avalanches were reported. They were triggered naturally and with the use of explosives. They stepped down to a deeply buried weak layer of facets. These avalanches were triggered at the upper end of treeline and in the alpine and were mostly in cross-loaded terrain features on west and northwest aspects.
On Wednesday, a skier accidental size 2 wind slab avalanche was triggered near St. Mary's. The avalanche occurred on a northeast aspect at treeline and stepped down to the basal facets. For photos and details check out the MIN report.
Snowpack Summary
Above 1400 m there is 20 to 40 cm of wind-affected snow that fell last week. It sits on a thin sun crust on solar slopes and wind-affected snow in open areas. A sun crust is found on the surface of solar slopes at all elevations.
In the Purcells around St Mary's, several weak layers from January and February can be found down 50 to 120 cm. The mid-snowpack is generally well-settled.
The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. This weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.
Weather Summary
Sunday Night
Mostly cloudy with clear periods, no accumulation, winds southeast 10 km/h, treeline temperatures -5 to 0 °C.
Monday
Cloudy with sunny periods, no accumulation, winds east 15 km/h, freezing levels 1700 m.
Tuesday
A mix of sun and cloud, no accumulation, winds east northeast 20 km/h, freezing levels 1000 to 1500 m.
Wednesday
Sunny with cloudy periods, no accumulation, winds northwest 20 km/h, freezing levels up to 2000 m.
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.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
Problems
Wind Slabs
Southwest winds have redistributed storm snow from earlier in the week building wind slabs in alpine and treeline lees. Although natural avalanche activity has tapered off wind slabs remain possible to human trigger.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The base of the snowpack remains very weak. Very large human triggered avalanches are possible at treeline and above. Avoid thin, rocky start zones and shallow areas with variable snowpack depths where you are most likely to trigger this layer.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 20th, 2023 4:00PM
