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Avalanche Forecast

Archived

Feb 1st, 2024–Feb 2nd, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

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

The avalanche cycle resulting from this week's very warm temperatures is now over, and the recovery has begun. Cooling temperatures will quickly improve the avalanche danger, but backcountry travel conditions are brutal: breakable crust. Hope is on the way this weekend though, as a 10 cm storm is forecast and the rebuild can begin.

Confidence

High

Avalanche Summary

No new avalanches were reported at the ski areas or in the backcountry on Thursday. The avalanche cycle from the past week is essentially over. The snowpack has yet to recover, but thin crusts forming on the surface by Thursday morning have begun the healing process.

Snowpack Summary

Warm temperatures and rain at low elevations over the past week created moist surface snow up to at least 2400 m, which will begin to freeze overnight Thursday and result in a strong melt-freeze crust forming on the snow surface (rugged travel conditions). The impact of this warming on the snowpack layering has yet to be evaluated, but expect the snowpack strength to increase dramatically as it refreezes.

Weather Summary

Temperatures are falling and will rapidly cool off starting Friday and more on Saturday under cloudy skies. By Saturday morning, expect valley bottom temperatures of -6 and alpine temperatures of -10. Winds will be light and switch to the north on Saturday bringing 5-10 cm of snow for the main part of the region over the weekend. Southeast areas (upslope) could see up to 25 cm with relatively light winds.

Terrain and Travel Advice

  • Avoid areas where the snow feels stiff and/or slabby.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.