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Avalanche Forecast

Archived

Mar 30th, 2023–Mar 31st, 2023

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.
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.

Two issues: snowpack structure and heating. The shallow snowpack structure is poor, which is why the danger ratings remain elevated. Sun and heat will increase the danger, usually in the afternoon when the crusts have melted, but with clouds rolling in on Friday this will become less of an issue.

Confidence

Moderate

Avalanche Summary

Our field team observed a 1-2 day old size 2.5 deep persistent slab on Dolomite peak today. Ski hills reported a warm day, but the snow surface remained mostly cool except on steep solar aspects. But, currently, it's 4 pm and the sun is high for a few more hours...

Snowpack Summary

Surface crusts exist to ridgetop on solar aspects. On polar aspects, 10-25cm of storm snow sits over a facetted interface from March 25th and buried temperature crusts below 1500 m. The lower snowpack remains weak, with depth hoar producing sudden test failures in many locations.

Weather Summary

The ridge of high pressure that has dominated the weather pattern this week is breaking down overnight and we can expect a change starting Friday. The weather switches to a SW flow, the wind will increase to 40 km/hr and a few flurries are expected and we might get 5 cm by Saturday. Freezing levels are forecasted to be about the same: 1500-2000 m.

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.