Avalanche Forecast

Archived

Mar 5th, 2023–Mar 6th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

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.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Banff Yoho Kootenay, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

We have decided to split the forecast region to reflect different conditions in the Little Yoho region versus thinner snowpack areas in the rest of the Banff, Yoho & Kootenay forecast area. Make sure to read the bulletin that is accurate for whichever region you plan to go to by clicking on the location of your planned trip on the map.

Confidence

Moderate

Avalanche Summary

Continued evidence of reactivity in the region:

Sunshine Village reported several explosives triggered avalanches to size 2.5 in west facing treeline terrain that had not been previously worked in.

A fresh size 3 skiier triggered avalanche was observed on a southern aspect of Mt. Fairview.

Snowpack Summary

The alpine and exposed regions at treeline are wind effected and have windslabs which are slowly becoming less reactive. Steep solar slopes at treeline and below may also have a thin sun crust. The wind slabs overlie the various Jan PWL interfaces of sun crusts, facets, and surface hoar down 40-80 cm. The weaker Nov. 16 basal facet layer is down 50-120 cm and produces moderate to hard sudden collapse results.

Weather Summary

A stable weather pattern over the next few days with treeline highs ~ -8 and overnight lows near -20. Winds will be generally calm to light from the SW through SE. Partly cloudy skies clearing Tuesday/ Wednesday.

For a more detailed weather forecast, click here.

Terrain and Travel Advice

If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

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.