Avalanche Forecast

Archived

Mar 1st, 2023–Mar 2nd, 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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

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

Snow and wind is forecast over the next few days. Expect a small increase in the avalanche danger until the weather calms down again.

Confidence

Moderate

Avalanche Summary

Forecasters investigated a size 2 skiier remote avalanche from yesterday in the Wild West area at Sunshine Village. This failed 65 cm down on one of the January PWLs.

Otherwise, Lake Louise ski hill reported triggering a few small windslabs in alpine terrain and Sunshine snow safety team observed a size 1.5 naturally triggered windslab out of north facing alpine terrain.

Snowpack Summary

Wind slabs are present in the alpine and at treeline. These wind slabs overlie the various Jan PWL interfaces of sun crusts, facets, and surface hoar down 80-120 cm. The weaker Nov 16 basal facet layer is down 100-200 cm, and produces moderate to hard sudden collapse results. Deeper snowpack areas west of the divide are stronger and more supportive than areas to the east.

Weather Summary

A system is moving in from the Alaskan Gulf on Thursday, followed by convective flurries for Friday, tapering Saturday. We should see ~ 2 cm by Thursday AM.

Thursday: ~ 5 cm. Alpine winds strong from the SW. Treeline temperatures -5 to -10.

Friday: ~ 5 cm. Alpine winds moderate from the W. Treeline temperatures -8 to -10.

Saturday: Light south alpine winds. Low near -20 in the AM. Light flurries in the afternoon.

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.