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Avalanche Forecast

Archived

Jan 31st, 2024–Feb 1st, 2024

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
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 widespread avalanche cycle over the past 72 hours has slowed. One more day of elevated freezing levels on Thursday will mean having some patience until things cool off, which should happen on the weekend.

Confidence

No Rating

Avalanche Summary

Previous widespread avalanche activity has occurred over the past 72 hrs. This includes natural wet loose avalanches up to size two on all aspects below treeline and on some steep solar aspects at higher elevations, and natural and explosive triggered avalanches up to size 2.5 failing on various facet, crust and basal facet weak layers at treeline and above. Avalanche control on Mt. Field Wednesday did not produce many avalanches, and overall activity has slowed.

Snowpack Summary

Previous rain and current warm temperatures have soaked the snowpack up to 2200 m, with moist surface snow even higher. Strong SW winds are creating wind slabs in alpine/treeline areas. Jan 19 facets from the cold snap are 10-30 cm deep, with the Dec 31 surface hoar/sun crust 30-50 cm deep. Two crusts (Dec 22 and Dec 5) exist in the mid-pack up to 2300m. The lower snowpack comprises weak facets and depth hoar in most areas. Treeline snow depths range from 70 -120 cm.

Weather Summary

Thursday - Freezing levels 2300-2400m with decreasing SW winds and mainly cloudy.

Friday - Freezing levels 1800-2000m with light SW winds and some flurries

Saturday - Freezing levels near valley bottom with some light to moderate snow amounts and light NE winds

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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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.