Avalanche Forecast

Archived

Mar 28th, 2023–Mar 29th, 2023

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.

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.

Direct sun and rising freezing levels could weaken the snowpack on southerly aspects.

Be aware of step-down failures into deep persistent weak layers.

Approach shallow rocky areas with caution.

Confidence

Moderate

Avalanche Summary

We suspect that wet loose avalanches occurred Tuesday on south aspects throughout the region, as conditions were clear and sunny.

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

While activity may have started to taper off on the deeper layers, some locations in the region (especially thin, rocky areas in the alpine) are still of concern.

Snowpack Summary

At upper elevations, up to 15 cm of recent snow was received since Saturday. This 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

The region will be under a building ridge of high pressure, with calm and dry conditions for the next few days.

Tuesday night

Clear with cloudy periods. Low alpine temperatures of -9 °C. Light easterly ridge wind. Freezing level at valley bottom.

Wednesday

Generally sunny. High alpine temperatures of -1 °C. Light easterly ridge wind. Freezing level rises to 2000 metres.

Thursday

A mix of sun and clouds. High alpine temperatures of -1 °C. Light westerly ridge wind gusting 30 km/h. Freezing level rises to 1800 metres.

Friday

Cloudy with sunny periods. Isolated flurries. High alpine temperatures of -3 °C. Moderate westerly ridge wind. Freezing level rises to 1800 metres.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Back off slopes as the surface becomes moist or wet with rising temperatures.
If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Minimize your exposure time below cornices.

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.