Avalanche Forecast
Issued: Mar 18th, 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 Loose Wet.
lbaker,
Avalanche Canada
Natural avalanche activity will be driven by the sun on Sunday. Minimize your exposure to steep slopes facing the sun during the hottest part of the day.
Stick to thick snowpack areas where you are less likely to trigger deep weak layers.
Summary
Confidence
High
Avalanche Summary
A snowmobile triggered a large persistent slab avalanche (size 2.5) in the south Purcells on Friday afternoon. 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, there were reports of several size 3 explosives triggered and natural wind slab avalanches that 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.
If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.
Snowpack Summary
20-40 cm of wind-affected storm snow falling earlier in the week can be found above 1400 m. This 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 Jan and Feb 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
Saturday Night
Clear skies. Treeline temperature -3 to -6 °C. Wind light northwest. Freezing levels remain elevated at 1400 m in the Purcells but drop to valley bottom in the Rockies.
Sunday
Mainly sunny with increasing clouds in the afternoon. Treeline temperature 0 °C. Wind light southeast. Freezing level rising to 2000m.
Monday
Mainly cloudy. Treeline temperature -4 °C. Wind moderate east. Freezing level 1600m.
Tuesday
Mix of sun and cloud. Treeline temperature -5 °C. Wind light east. Freezing level 1500m.
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
Loose Wet
Steep, rocky terrain facing the sun is likely to see thin loose wet avalanches release during the heat of the day.
Aspects: South East, South, South West, West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 19th, 2023 4:00PM
