Avalanche Forecast
Issued: Mar 22nd, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs.
zryan,
Avalanche Canada
Large human-triggered deep persistent slab avalanches remain possible. Stay diligent in your terrain selection by avoiding steep, rocky, wind-affected terrain and choosing small, low-consequence features.
Summary
Confidence
Avalanche Summary
On Monday, a size 1 natural cornice failure occurred in the St Mary's east of Kaslo. The cornice dropped onto a steep slope and gouged down to the weak facets at the base of the snowpack.
On Sunday, natural size 1 loose wet avalanches were observed from steep rocky terrain on solar aspects.
In the northern Purcells on Sunday, several large natural deep persistent avalanches were observed and in the nearby Pedley Pass, this MIN report describes what was expected to have been a remotely triggered slab that failed down 80 cm. While activity may have started to taper off on the deeper layers in this region, nearby avalanches are a reminder that the layers are likely still reactive in some locations in the region, especially thin, rocky areas in the alpine.
Snowpack Summary
The snow surface consists of a sun crust on solar aspects, small facets and surface hoar on shaded and wind-sheltered slopes, and wind-affected surfaces in exposed terrain.
An interface buried around March 11 sits down 30-40 cm and typically consists of a thin sun crust on solar slopes and wind-affected snow in exposed terrain.
In the Purcells around St Mary's, several weak layers from January and February can be found down 50-120 cm. These layers appear to have generally gone dormant but could still be reactive in isolated areas and should be on your radar in the Purcells part of the region.
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
Wednesday night
Clear. Alpine temperatures drop to a low of -6 °C. Ridge wind light from the southwest. Freezing level at valley bottom.
Thursday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of 0 °C. Ridge wind 10 to 30 km/h from the southwest. Freezing level rises to 2000 metres.
Friday
Mainly cloudy with scattered flurries, up to 5 cm of accumulation. Alpine temperatures reach a high of -4 °C. Ridge wind 10 to 35 km/h from the southwest. Freezing level rises to 1300 metres.
Saturday
Cloudy with sunny periods and isolated flurries. Alpine temperatures reach a high of -7 °C. Ridge wind 10 to 30 km/h from the southwest. Freezing level rises to 1100 metres.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Avalanche hazard may have improved, but be mindful that deep instabilities are still present.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- Avoid slopes when the solar radiation is strong, especially if they have large cornices overhead.
Problems
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. Give careful consideration to the slopes overhead as large avalanches may run well into the runout zone or into lower-angle terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 23rd, 2023 4:00PM
