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Avalanche Forecast

Archived

Dec 4th, 2023–Dec 5th, 2023

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

Regions

Purcells, South Rockies, Dogtooth, East Purcell, Moyie, St. Mary, Bull, Crowsnest North, Crowsnest South, Elkford East, Elkford West.

Conservative terrain travel is recommended, as snow and rain are expected to increase the danger.

Confidence

Moderate

Avalanche Summary

A few small to large (size 1 to 2) wind slabs were observed on Sunday, being triggered naturally and by riders. They occurred on north to east aspects and where 20 to 50 cm deep, releasing on the surface hoar and facet layer described in the Snowpack Summary.

Looking forward, snow and rain will continue to load these weak layers and increase the likelihood of triggering them.

Snowpack Summary

Snow is forecast to switch to rain between Monday night and Tuesday daytime. This will load a buried weak layer of feathery surface hoar and/or sugary faceted grains. These layers may be associated with a hard melt-freeze crust on sun-exposed slopes.

The middle and base of the snowpack is largely weak and faceted. A hard crust may be found near the ground. Treeline snowpack depths are variable and generally range between 30 and 80 cm. Snowpack tapers rapidly as you move lower in elevation.

Weather Summary

Monday Night

Cloudy with 5 to 15 cm of snow. Southwest alpine wind 20 to 40 km/h. Treeline temperature -4 °C. Freezing level 1500 m.

Tuesday

Cloudy with 5 to 15 cm snow above 2000 m and rain below. Southwest alpine wind 20 to 40 km/h. Treeline temperature 0 °C. Freezing level rising from 1500 m to 2500 m.

Wednesday

Cloudy with 5 to 15 cm snow above 1800 m and rain below. Southwest alpine wind 10 to 20 km/h. Treeline temperature 0 °C. Freezing level 1500 to 2000 m.

Thursday

Cloudy with 5 to 15 cm snow. Southwest alpine wind 10 to 20 km/h. Treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
  • Watch for signs of slab formation throughout the day.
  • Watch for areas of hard wind slab on alpine features.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Early season avalanches at any elevation have the potential to be particularly dangerous due to obstacles that are exposed or just below the surface.

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.

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.