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Avalanche Forecast

Archived

Mar 15th, 2023–Mar 16th, 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 possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

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

Hazard will rise to considerable in the alpine during peak daytime heating.

Avoid thin areas like rock outcroppings where you are most likely to trigger deep persistent layers.

Confidence

High

Avalanche Summary

On Wednesday, a skier accidental size 2 wind slab avalanche was triggered near St. Mary's. The avalanche occurred on a northeast aspect at treeline and stepped down to the basal facets. For photos and more details check out the MIN.

On Tuesday, several natural size 2 wind slab avalanches were observed throughout the region at alpine and treeline. A size three natural avalanche was reported north of Sparwood. The start zone of the avalanche was a steep, rocky, cross-loaded alpine feature. It is suspected to have been a deep persistent slab avalanche.

If you head out in the backcountry, let us know what you are seeing by submitting a report to the Mountain Information Network.

Snowpack Summary

20-40 cm of wind-affected storm snow is found above 1400 m. The storm snow sits on a thin sun crust on solar slopes and wind affected snow in open areas. Below 1400 m a rain crust covers the surface.

In the Purcells, several weak layers from Jan and Feb can be found down 50 to 120 cm however they are showing signs of strengthening. 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

Few clouds clear through the night. Chance of isolated flurries, trace accumulation. Alpine temperatures reach a low of -8 °C. Ridge wind 10 km/h gusting to 30 km/h from the northwest. Freezing levels drop to valley bottom.

Thursday

Mainly sunny with scattered clouds in the afternoon. Alpine temperatures reach a high of -4 °C. Ridge wind west 10 km/h. Freezing levels rise to 1700 meters.

Friday

Mainly sunny. Alpine temperatures reach a high of -2 °C. Ridge wind southwest 15 km/h. Freezing levels rise to 1800 meters.

Saturday

Sunny. Alpine temperatures reach a high of 0 °C. Ridge wind southwest 20 km/h. Freezing levels rise to 2000 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.

Problems

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.

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.