Avalanche Forecast
Issued: Mar 23rd, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Deep Persistent Slabs and Loose Dry.
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
Moderate
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.
Last Sunday In the northern Purcells, 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.
If you have any observations from this data sparse region, let us know what you are seeing by submitting a report to the Mountain Information Network.
Snowpack Summary
Up to 15 cm of new snow may accumulate at upper elevations by end of day Friday. This new snow overlies 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
Thursday night
Clear periods. Alpine temperatures drop to a low of -7 °C. Mostly Ridge wind 10 to 35 km/h from the southwest. Freezing level at valley bottom.
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 1400 metres.
Saturday
A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -4 °C. Ridge wind light from the northwest. Freezing level rises to 1500 metres.
Sunday
Flurries, 5-10 cm of accumulation. Alpine temperatures reach a high of -5 °C. Ridge wind light from the east. Freezing level rises to 1500 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.
- It's critical to stay disciplined and choose only well supported, low consequence lines.
- Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
- Watch for signs of slab formation throughout the day.
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.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Loose Dry
New snow is expected to bond poorly to the underlying surface, creating small but reactive dry loose avalanches. In isolated areas that receive greater than 15 cm of new snow, it is possible that a storm slab problem may exist in steep terrain.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Mar 24th, 2023 4:00PM
