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Avalanche Forecast

Archived

Apr 4th, 2025–Apr 5th, 2025

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
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 possible, human triggered probable.
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, Banff, East Side 93N, Kootenay, Lake Louise, LLSA, Sunshine, West Side 93N, Field.

Solar heating has already exerted significant impacts on the snowpack this week. A bigger punch is forecast to arrive Saturday which may have the biggest effect yet.

While the dry snow on higher, north slopes will draw travelers this weekend, be warned that this is also where the risk of triggering the persistent slab is the greatest.

Confidence

Moderate

Avalanche Summary

Lake Louise avalanche control triggered a size 2 deep persistent slab with explosives in a piece of north-facing terrain above Lipalian 3 just above treeline Thursday.

Snowpack Summary

Surface crusts on solar aspects up to ~2800 m. Up to 30 cm of dry snow on north slopes at higher elevations. On southerly aspects, this 30cm contains several crusts.

Below this, a prominent rain crust (Mar 27) is found everywhere up to at least 2300m. The strength and extent of this crust varies area to area.

Below this, a 70 cm slab of dense snow overlies another 70 cm of weak facets. This is the main problem in the snowpack and is of particular concern when the crusts above it are weak

Weather Summary

Solar heating is the most important input right now.

A ridge brings light to moderate west winds under clear skies through Sunday night.

Overnight lows Friday night near treeline will be near -10C with the freezing level climbing to near 2500m Saturday afternoon.

While the winds may be enough to discourage the effects of solar inputs in higher, open areas, expect moist snow on sheltered steep slopes

Terrain and Travel Advice

  • Be mindful that deep instabilities are still present and have produced recent large avalanches.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Avoid steep, sun-exposed slopes when the air temperature is warm or when solar radiation is strong.
  • Start your day early and be out of avalanche terrain during the heat of the day.
  • Avalanche danger will increase as the surface crust breaks down.

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.

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.