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Avalanche Forecast

Archived

Mar 17th, 2023–Mar 18th, 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 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.

There is uncertainty with the freezing level and the amount of cloud cover on Saturday. Certainly if the sky remains clear we may see the warmest day this week. Minimize your exposure to steep slopes facing the sun during the hottest part of the day.

Confidence

High

Avalanche Summary

On Thursday in the Elk Valley there were reports of several size 3 explosives triggered and natural wind slab avalanches that stepped down to a deeply buried weak layer of facets. These avalanche were triggered at the upper end of treeline and in the alpine and were mostly in cross-loaded terrain features on west and northwest aspects.

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 report.

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 falling earlier in the week can be found above 1400 m. This 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 around St Mary's, several weak layers from Jan and Feb can be found down 50 to 120 cm. 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

Friday Night

Mainly clear. Treeline temperature -9 °C. Wind light southwest. Freezing level at valley bottom.

Saturday

Mainly sunny with cloudy periods. Treeline temperature near 0 °C. Wind light southwest. Freezing level rising to 2000m.

Sunday

Mix of sun and cloud. Treeline temperature -1 °C. Wind light southeast. Freezing level rising to 2000m.

Monday

Mainly cloudy with scattered flurries. Treeline temperature -4 °C. Wind light east. Freezing level 1500m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be especially cautious as you transition into wind affected terrain.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.