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Avalanche Forecast

Archived

Apr 23rd, 2023–Apr 24th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Lizard-Flathead, South Rockies, Akamina, Flathead, Lizard, Moyie, Bull, Crowsnest North, Crowsnest South, Elkford East, Elkford West.

High daytime freezing levels and mild overnight temperatures will stress the snowpack, with the greatest hazard 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.

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 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.

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.

Around 20-50 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.

A weak layer of large, sugary crystals persists at the base of the snowpack. This layer has not produced recent avalanche activity in these areas, but it is a concern as warming affects the snowpack - particularly in thin and rocky snowpack areas.

Weather Summary

Sunday Night

Mostly cloudy. Light snowfall delivers around 5-10 cm. Light westerly wind. Freezing levels remain above 1500 m overnight.

Monday

Cloudy with light westerly winds. Isolated flurries may deliver up to 10 cm in localised areas. Freezing levels reach 2200 m, so expect mixed precipitation or rain below.

Tuesday

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

Wednesday

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

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Watch for signs of instability like whumpfing, hollow sounds, shooting cracks or recent avalanches.
  • 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

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.