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Avalanche Forecast

Archived

Dec 5th, 2023–Dec 6th, 2023

Alpine
Natural and human triggered avalanches likely.
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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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

Conservative terrain travel and avoidance of alpine terrain is recommended. Riders could trigger slabs at higher elevations or loose avalanches at lower elevations.

Confidence

Moderate

Avalanche Summary

Widespread natural avalanche activity was observed Monday night and on Tuesday during the warm stormy conditions. Storm slabs are releasing at high elevations and loose wet at lower elevations. We may see similar activity continue on Wednesday, as more snow and rain load the buried weak layer described in the Snowpack Summary.

Snowpack Summary

Around 10 to 20 cm of heavy snow accumulated at high elevations, with rain soaking the snowpack below. The snow and rain are loading 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

Tuesday Night

Cloudy with 10 to 25 cm of snow above 1800 m and rain below. Southwest alpine wind 20 to 40 km/h. Treeline temperature 0 °C. Freezing level 2000 m.

Wednesday

Cloudy with 5 to 15 cm of snow above 1700 m and rain below. Southwest alpine wind 20 to 30 km/h. Treeline temperature 0 °C. Freezing level 1900 m.

Thursday

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

Friday

Mix of sun and cloud with trace snow. Southwest alpine wind 10 to 20 km/h. Treeline temperature -7 °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.
  • 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.