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Avalanche Forecast

Archived

Feb 28th, 2024–Feb 29th, 2024

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

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

We are in the midst of a widespread avalanche cycle! Avoid all avalanche terrain.

Mt. Stephen, Mount Bosworth, and Sunshine Road avalanche closure zones are CLOSED on Thursday, Feb 29th.

Confidence

High

Avalanche Summary

Forecasters have observed continued evidence of a widespread avalanche cycle following the recent storm. This cycle is expected to continue through Thursday as we receive more snow and wind.

Avalanche control on Mt Whymper (Kootenay NP) on Tuesday produced size 2-3 avalanches with every shot. The crowns were 40-100 cm deep and the failure planes were the recent storm snow sliding on the Feb. 3rd crust and occasionally stepping down to ground.

Snowpack Summary

New wind slabs are forming on lee aspects at ridgetop. 30-60 cm of recent snow sits on top of the Feb 3rd crust/ facet layer. This crust is variable in thickness and exists up to 2500m (higher on solar aspects). In thinner eastern areas, the mid and lower snowpack are weak and facetted.

Average snowpack depths at treeline range from 80 cm in thinner eastern areas to 160 cm in thicker western areas.

Weather Summary

With the low tracking into southern Alberta and deepening slightly on Thursday, the snow will intensify over the Rockies.

Wednesday Night: Periods of snow ~15 cm. Low -6 °C in the alpine. Ridge wind southwest: 20 km/h gusting to 55 km/h. Freezing level at valley bottom.

Thursday: Flurries ~20cm new snow. High -5 °C in the alpine. Mostly light ridge wind, gusting 55km/h.

Click here for a more detailed weather forecast

Terrain and Travel Advice

  • Avoid all avalanche terrain during periods of heavy snowfall.
  • Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.