Avalanche Forecast
Issued: Apr 22nd, 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
Although avalanche danger ratings are once again decreasing, buried weak layers remain a lower probability, but high consequence problem.
Use extra caution in areas that experience warm temperatures combined with strong sunshine. These factors will stress a weak snowpack.
Summary
Confidence
Avalanche Summary
Observations are limited at this point in the season. If you have any information, let us know what you are seeing through the Mountain Information Network.
On Thursday and Friday, loose wet avalanches were observed, naturally triggered by the sun. Explosive control work on Thursday produced size 1 avalanches within the recent storm snow, shallow but up to 100 m wide.
Reported activity on the persistent and deep persistent weak layers has tapered off within the last two weeks. The Western Purcells have seen more recent human-triggered activity, including explosive-controlled avalanches and a fatal size 3 on April 15th in the Thunderwater Lake area. This indicates the potential for triggering, although decreased, is still present with high consequences. Continue to avoid rocky start zones for the remainder of the season.
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
Saturday Night
Some cloud, with isolated flurries delivering trace amounts of snow. Light to moderate westerly wind. Freezing levels drop to 1000 m overnight.
Sunday
Mostly cloudy with sunny periods and isolated flurries. Moderate westerly wind. Freezing levels rise to 2200 m, and remain above 1500 m overnight.
Monday
Clouds clear in the afternoon with light westerly winds. Isolated flurries. Freezing levels reach 2200 m.
Tuesday
A mix of sun and cloud with light westerly winds. No snowfall expected. Freezing levels rise to 2200m.
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 23rd, 2023 4:00PM
