Avalanche Forecast

Archived

Apr 20th, 2023–Apr 21st, 2023

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Below Threshold.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Below Threshold.

Regions

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

Moderate avalanche danger means there is still heightened avalanche conditions on specific terrain features and that human triggered avalanches are still possible. If you are going to step out - do so with caution.

Confidence

Moderate

Avalanche Summary

On Tuesday several small wind slabs in the alpine were observed. Also one large avalanche stepping down to ground from a falling cornice occurred on Big Bend Peak.

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

Friday

A mix of sun and cloud.

Alpine temperature: High -3 °C.

Ridge wind light to 15 km/h.

Freezing level: 1800m

Saturday

Cloudy with sunny periods and isolated flurries.

Precipitation: Trace.

Alpine temperature: Low -7 °C, High -2 °C.

Mostly light ridge wind gusting to 25 km/h.

Freezing level: 2000m

Look for weather products and tutorials at Avalanche Canada.

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.

Problems

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.