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Avalanche Forecast

Archived

Mar 26th, 2023–Mar 27th, 2023

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

Regions

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

Human triggering of the persistent and deep persistent layers remains the main concern. Watch for a weakening of the snowpack due to solar heating and possible heat triggered cornice failures when the skies clear over the next few days.

Confidence

Moderate

Avalanche Summary

A couple of skier triggered avalanches were reported on Saturday in the Massive Mountain and Observation Sub Peak areas. These failed on layers down 25-100 cm and show that human triggering of various buried layers is still possible.

Snowpack Summary

5-10 cm of storm snow sits over buried temperature crusts to 1500 m, sun crusts to ridgetop on solar aspects, and facets on shaded slopes. The midpack in this area has several crust and facet layers 30-110 cm down, that remain a concern in steep terrain. The bottom of the snowpack consists of weak basal facets in many areas, with sudden test failures still occuring on these facets.

Weather Summary

Scattered light flurries with a couple cm's of new snow Sunday night into Monday morning. A clearing trend starts mid-day on Monday as a high pressure system moves into the area. Alpine highs between -5 and -8°C with light NW winds are forecast. Clear skies and cool temperatures Monday night with sunshine expected on Tuesday and Wednesday.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Cornices become weak with daytime heating or solar exposure.

Problems

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.

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.