Avalanche Forecast

Issued: Apr 23rd, 2023 4:00PM

The alpine rating is considerable, the treeline rating is considerable, and the below treeline rating is moderate. Known problems include Persistent Slabs and Deep Persistent Slabs.

Avalanche Canada wlewis, Avalanche Canada


High daytime freezing levels and mild overnight temperatures will continue to stress an already weak snowpack.

Stick to conservative, low angle, and supported terrain features. Avoid thin and rocky terrain where warming will be most intense.




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.

Loose wet avalanches were observed this week, 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 on the most recent buried crust.

The numerous buried weak layers including the basal facets remain a concern, especially as warm temperatures stress the snowpack this week. Recent avalanche activity on these layers in adjacent forecast areas highlights the need to avoid rocky and thin snowpack areas for the remainder of the season.

  • A fatal size 3 was reported from the Lake Louise area on April 22nd, in a particularly thin and rocky area with a 50 cm deep snowpack. All information can be found here.

  • The Western Purcells have reported recent human-triggered activity, including a fatal size 3 on April 15th in the Thunderwater Lake area near a rocky feature, the avalanche was 40-100 cm deep. More information can be found here.

Snowpack Summary

Mild temperatures and sunshine have created a surface crust that exists on all aspects on sun-affected slopes and into the alpine on shaded slopes. Moist snow likely remains at low elevations on all aspects.

Recent wind-affected storm snow then sits overs 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.

The mid snowpack is generally settled and strong. However, 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.

Continued warm temperatures this week are expected to stress these buried weak layers, making them more sensitive to triggers. We are concerned about the potential for very large avalanches on the basal facet layer as temperatures remain warm overnight, limiting recovery within the snowpack.

Weather Summary

Sunday Night

Mostly cloudy with isolated flurries. Light westerly wind. Freezing levels remain above 1500 m overnight.


Clouds clear in the afternoon with light westerly winds. Isolated flurries with light rain at lower elevations. Freezing levels reach 2200 m.


A mix of sun and cloud with light westerly winds. No snowfall is expected. Freezing levels rise to 2200m.


Mostly clear skies with moderate westerly winds. No snowfall expected.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.


Persistent Slabs

An icon showing Persistent Slabs

Several crust layers exist in the upper snowpack, producing avalanches in nearby regions.

Use extra caution around ridgelines 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.


Possible - Likely

Expected Size

1 - 2.5

Deep Persistent Slabs

An icon showing Deep Persistent Slabs

The base of the snowpack remains very weak. Deep persistent slab avalanches continue to be reported in this area and adjacent forecast areas with similar snowpack structures.

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.



Expected Size

2.5 - 4

Valid until: Apr 24th, 2023 4:00PM