Avalanche Forecast
Issued: Apr 21st, 2023 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Persistent Slabs and Deep Persistent Slabs.
wlewis,
Avalanche Canada
Recent snowfall has added load to more buried weak layers, steer clear of thin and rocky start zones.
Head to well-supported terrain features and manage your exposure to sun-affected slopes if skies clear.
Summary
Confidence
Moderate
Avalanche Summary
On Thursday, loose wet avalanches were observed to size 1, naturally triggered by the sun. Explosive control work produced size 1 avalanches within the recent storm snow, shallow but up to 100 m wide.
A fatal size 3 avalanche occurred on April 15th in the Thunderwater Lake area, just west of this region. The avalanche was triggered near a rocky area, involving a storm snow instability on an April crust. All information on this incident can be found here.
If you are getting out in the backcountry, consider posting on the MIN.
Snowpack Summary
At treeline and above, recent snow is being redistributed by variable winds into deeper deposits likely found on many aspects. This overlies a variety of crust, surface hoar, and/or facet layers buried from mid-March through early April. These layers have produced recent avalanche activity in nearby regions and continue to be monitored here. Below treeline, expect to find moist or refrozen surfaces, and shrinking snowpack depths.
The mid snowpack is generally settled and strong. The lower snowpack includes a widespread layer of large, weak facets and/or depth hoar crystals. This weak layer has been responsible for several very large and destructive avalanches throughout the season. This layer continues to be a concern, especially during times of rapid loading or prolonged warming.
Weather Summary
Friday Night
Mainly cloudy with isolated flurries, 1-5 cm of snow possible. Light to moderate west wind. Freezing levels drop to 500 m overnight.
Saturday
Mainly cloudy with isolated flurries, and trace accumulations of snow. Light westerly wind. Freezing levels rise from valley bottom to 2000 m.
Sunday
Mostly cloudy with sunny periods and isolated flurries, 1-5 cm possible. Moderate westerly wind. Freezing levels rise to 2100 m by mid-day.
Monday
A mix of sun and cloud with light westerly winds. Flurries possible. Freezing levels remain around 2000 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Brief periods of sun could quickly initiate natural avalanche activity.
- Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
- Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
- Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
Problems
Persistent Slabs
Several crust layers exist in the upper snowpack, producing avalanches in nearby regions.
Use extra caution around ridgecrest and on convex slopes. Retreat to mellower terrain (think low angle, low exposure) if you find signs of instability like shooting cracks, whumpfs, or recent avalanches.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Deep Persistent Slabs
The base of the snowpack remains very weak. Deep persistent slab avalanches continue to be reported in this forecast area throughout the season.
This is a low-probability/high-consequence avalanche problem as this layer is deeply buried near the ground. Avoid thin, rocky start zones and shallow areas with variable snowpack depths.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Apr 22nd, 2023 4:00PM
