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Archived

Avalanche Forecast

Apr 20th, 2023–Apr 21st, 2023
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
3: Considerable
The avalanche danger rating at treeline will be considerable
Below Treeline
Below Threshold
The avalanche danger rating below treeline will be below threshold

Regions: Brazeau, Churchill, Cirrus-Wilson, Fryatt, Icefields, Jasper, Maligne, Marmot, Miette Lake, Pyramid.

Isolated large to very large avalanches are still possible in moderate avalanche danger. Recent large cornice triggered deep persistent slabs are a good reminder to keep your head on a swivel when stepping out into a more complex terrain.

Confidence

Moderate

Avalanche Summary

On Friday , 2 natural large deep persistent slab avalanches were observed by the Icefields road patrol, both on east aspect in the alpine triggered by a cornice failure.

Maligne road patrol saw no new natural avalanche activity on Friday.

Don't forget to post avalanche observations to the MIN.

Snowpack Summary

Around 15cm of new snow this week sits on crusts on solar aspects, a melt freeze crust below tree line and old wind slab in exposed alpine

Below tree line is in a daily melt-freeze cycle. At tree line the mid-pack consists of multiple layers of sun crusts or facets. Depth hoar and basal facets at the base.

Weather Summary

Saturday: Cloudy with sunny periods. Precipitation: Nil. Alpine temperature: High -2 °C. Ridge wind light to 20 km/h. Freezing level: 2000 m.

Sunday: Cloudy with sunny periods and isolated flurries. Precipitation: Trace. Alpine temperature: Low -4 °C, High 1 °C. Mostly light ridge wind occasionally gusting to 25 km/h. Freezing level: 2400 m.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Cornices become weak with daytime heating.

Avalanche Problems

Cornices

With increasing daytime temperatures and sun effect mature cornices have a potential to trigger the lingering deep persistent slab below.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine.

Likelihood: Possible

Expected Size: 2 - 3

Deep Persistent Slabs

The bottom of the snowpack is inherently weak with well-developed Facets and Depth Hoar.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 4

Persistent Slabs

Several persistent weak layers in the midpack can be found as facets on polar aspects and sun crusts on solar aspects.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1.5 - 3