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Avalanche Forecast

Archived

Mar 14th, 2023–Mar 15th, 2023

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

Storm snow and strong southwest winds have created dangerous avalanche conditions in the alpine. Use extra caution when transitioning into wind affected terrain, where storm slabs remain reactive to human triggering.

Avoid thin, rocky, wind effected areas where triggering slabs is more likely. If triggered storm slabs may step down to deep weak layers resulting in large destructive avalanches.

Confidence

High

Avalanche Summary

On Monday, a few 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

The Purcells received 30-40 cm of storm snow while the Rockies received 10-15 cm of storm snow over the last few days. Storm snow covers a variety of surfaces including hard wind-affected surfaces in open areas, a sun crust on steep solar aspects, and facetted snow in sheltered areas.

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

Tuesday Night

Mainly clear skies. Alpine temperatures reach a low of -9 °C. Ridge wind 15 km/h from the southwest. Freezing levels drop to valley bottom.

Wednesday

Mainly cloudy with sunny periods. Alpine temperatures reach a high of -6 °C. Ridge wind 10 km/h gusting to 30 km/h from the northwest. Freezing levels rise to 1400 meters.

Thursday

Mainly sunny. Alpine temperatures reach a high of -5 °C. Ridge wind variable 10 km/h. Freezing levels rise to 1500 meters.

Friday

Mainly sunny. Alpine temperatures reach a high of -3 °C. Ridge wind southeast 15 km/h. Freezing levels rise to 1700 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded terrain features.
  • 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

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.