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

Regions

South Rockies, St. Mary, Bull, Elkford East, Elkford West.

Convective snowfalls could bring localized heavy precipitation, especially in higher terrain.

Uncertainty remains about the total accumulation from these enhanced precipitations.

This new snow will likely bond poorly to the underlying surfaces and be reactive to riders.

Confidence

Moderate

Avalanche Summary

Several dry loose avalanches (size 1) were naturally triggered within the recent snow on steep northerly alpine features near St.Mary's on Saturday.

On Wednesday, a very large natural deep persistent was observed north of Elkford. This avalanche occurred on a southwest aspect in the alpine, likely as a result of strong solar radiation. It ran to valley bottom and took out the Smith Basin trail.

Last Monday, a natural cornice failure resulted in a size 1 avalanche in the St Mary's area east of Kaslo. The cornice dropped onto a steep slope and gouged down to the weak facets at the base of the snowpack.

While activity may have started to taper off on the deeper layers, nearby avalanches are a reminder that the layers are likely still reactive in some locations in the region, especially thin, rocky areas in the alpine.

Snowpack Summary

At upper elevations, up to 15 cm of recent snow overlies a crust on solar aspects, faceted snow and surface hoar up in shaded and wind-sheltered areas. Wind-affected surfaces are found in exposed areas. At lower elevations, a crust exists on or near the surface.

In the middle of the snowpack, there are at least a couple of lingering persistent weak layers, including surface hoar in wind-sheltered terrain and a sun crust on south aspects. These layers appear to have generally gone dormant but could still be reactive in isolated areas and should be on your radar in the Purcells part of the region.

The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. This weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.

Weather Summary

Unsettled weather will continue to bring scattered flurries until a ridge of high pressure invades the region early next week. Enhanced precipitations are expected in higher terrain Sunday night and Monday.

Sunday night

Cloudy. Isolated flurries. Local amounts of 5-10 cm and up to 15 cm in higher ground. Low alpine temperatures of -7 °C. Light southeasterly ridge wind. Freezing level at valley bottom.

Monday

Cloudy with sunny periods. Lingering flurries. High alpine temperatures of -5 °C. Light southwest ridge wind. Freezing level rises to 1500 metres.

Tuesday

A mix of sun and clouds. High alpine temperatures of -3 °C. Light easterly ridge wind. Freezing level rises to 1500 metres.

Wednesday

A mix of sun and clouds. High alpine temperatures of -2 °C. Light easterly ridge wind. Freezing level rises to 1800 metres.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Loose avalanches may start small but they can grow and push you into dangerous terrain.
  • It's critical to stay disciplined and choose only well supported, low consequence lines.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
  • Minimize your exposure time below cornices.

Problems

Loose Dry

Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

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.