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Avalanche Forecast

Archived

Mar 28th, 2023–Mar 29th, 2023

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

Strong solar input will continue Wednesday. Avoid exposure to sun-exposed slopes, especially late in the day. Now is the time to make the habit of starting the day early, and finishing early.

Confidence

Moderate

Avalanche Summary

On a road patrol to Kootenay, deep slabs up to size 3 were observed on Mt Whymper and the Tumbling Peak area. These slides occurred within the last 24 hours. Solar radiation is a possible trigger.

Snowpack Summary

10-25cm of storm snow from the last 4 days 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, which remain a concern in steep terrain. The bottom of the snowpack consists of weak basal facets in many areas, with sudden test results still occurring.

Weather Summary

On Wednesday, light and variable wind, a mix of sun and cloud, and cool radiant air temps (valley high of 5 deg and alpine -10) are expected. Solar radiation could be intense, despite cool-ish radiant air temperatures.

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.

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.