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Avalanche Forecast

Archived

Mar 8th, 2023–Mar 9th, 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, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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

Avoid shallow rocky terrain where the snowpack transitions from thick to thin and triggering the deep persistent layer is more likely.

Confidence

Moderate

Avalanche Summary

On Monday, a few natural, size three avalanches were observed in the region. A cornice triggered a wind slab avalanche on a steep rocky north-facing slope in the Selkirks. In the Rockies, a deep persistent slab avalanche was triggered by a cornice or solar input in extreme, rocky terrain. See the MIN for a photo.

Snowpack Summary

40-50 cm of storm snow from earlier in the week sits over wind affected surfaces in sheltered locations. Wind slabs may be found on all aspects due to variable winds in the past few days. A melt-freeze crust covers the surface of steep solar slopes.

The mid-snowpack is generally well settled. 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

Wednesday Night

Partly cloudy. Easterly ridgetop winds 15-25 km/h. Treeline temperatures, low of -15.

Thursday

A mix of sun and cloud with isolated flurries, trace accumulation. Southerly winds 15-25 km/h. Treeline temperatures, high of -10.

Friday

Cloudy with scattered flurries, 3-6 cm accumulation. Easterly ridgetop winds 15-25 km/h. Treeline temperatures, high of -10.

Overnight flurries continue 2-3 cm accumulation. Winds switch to the southwest 20 km/h.

Saturday

Partly cloudy with isolated flurries, trace accumulation. Southwest ridgetop winds 20 km/h. Treeline temperatures, high of -10.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid areas with a thin or variable snowpack.
  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.