Avalanche Forecast

Issued: Apr 24th, 2023 4:00PM

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

Avalanche Canada wlewis, Avalanche Canada

High daytime freezing levels and mild overnight temperatures will stress the snowpack, with the greatest concern for thin snowpack areas where buried crusts and weak layers may become reactive.

Stick to conservative, low-angle, and supported terrain features. Avoid overhead hazard during peak warming and sunshine.

Summary

Confidence

Moderate

Avalanche Summary

Observations are limited at this point in the season. If you have any observations, let us know what you are seeing through the Mountain Information Network.

Loose snow avalanches have been observed throughout the week as the sun weakens the surface snow.

Recent avalanche activity 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 near Lake Louise on April 22nd, in a particularly thin and rocky area with a 50 cm deep snowpack. All information can be found here.

Snowpack Summary

Warm temperatures will weaken the surface snow as freezing levels rise on Tuesday, breaking down surface crusts and moistening any previously dry snow to around 2500 m on all aspects. Sun-affected terrain will see the most intense warming, likely creating wet and slushy snow to mountain top.

Around 20-40 cm deep, a thick melt-freeze crust is found up to 2200 m. As temperatures increase this will become a concern for avalanche activity.

The mid snowpack is generally settled and strong at treeline and above. The exception is areas where snow depths measure less than 150 cm. In these thin areas, the mid-pack is likely weaker and more faceted. These areas will respond more rapidly to warming temperatures, becoming unstable.

A weak layer of large, sugary crystals persists at the base of the snowpack. This layer is a concern as warming affects the snowpack - particularly in thin and rocky snowpack areas.

Weather Summary

Monday Night

Mostly cloudy. Light westerly wind. Freezing levels drop to 1700 m. Flurries possible.

Tuesday

Mostly sunny with freezing levels rising to 2500 m. Treeline temperatures around +7 °C. Moderate westerly winds. No snowfall.

Wednesday

Mostly sunny with freezing levels rising to 2800 m. Treeline temperatures of +10 °C. Moderate westerly winds.

Thursday

Full sun with freezing levels heading towards 3000 m. Treeline temperatures above +10 °C. Light westerly winds.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • 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.

Problems

Loose Wet

An icon showing Loose Wet

Avoid slopes that have moist or wet surface snow in the afternoon when warming is expected to be most intense. Warming will be amplified on steep, sun-affected slopes around rocky outcrops.

Stick to shaded slopes earlier in the day if you choose to venture out, and head out of the backcountry before peak warming.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs

Multiple crusts exist throughout the snowpack that may form ideal sliding layers for avalanche activity as warm temperatures weaken the snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

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 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.

Uncertainty is high about how this layer will react to this warm weather and when it will reach the tipping point for large avalanche activity.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Apr 25th, 2023 4:00PM

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