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 possible, human triggered probable.

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 Columbia, Dogtooth, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold.

Snow and rain continue to place stressors on the snowpack.

Natural and human-triggered avalanches should be expected.

Confidence

Moderate

Avalanche Summary

Local operators produced numerous storm slab avalanches with the use of explosives on Monday.

Several size one to two natural and skier-triggered avalanches were reported in our region this past weekend. Many of these were remotely triggered and ran on the buried surface hoar layer. These avalanches occurred at treeline elevation and on all aspects.

Snowpack Summary

By Wednesday morning up to 40 mm of precipitation falling as rain and/or snow will have been added to the snowpack. This heavy load will be weighing on up to 40 cm of snow that fell this weekend. The layer of greatest concern, large buried surface hoar, can be found just below this recent snow.

On steep south-facing slopes, this surface hoar sits on a thin sun crust. At higher elevations, the weekend's snow will have formed wind slabs on north and east-facing slopes.

The mid-pack is generally well-settled. Lower in the snowpack a crust with sugary facets beneath it can be found 20 cm off the ground.

Weather Summary

Tuesday Night

Cloudy, 5 to 10 cm accumulation of rain and snow with up to 20 in the far east, alpine winds southwest 25 to 35 km/h, freezing level as high as 2000 m.

Wednesday

Mostly cloudy, 15 to 20 cm accumulation above 1500 m and rain in the valley, alpine winds westerly 25 to 35 km/h, freezing level at starting at 2000 m and decreasing throughout the day.

Thursday

Cloudy with possible sunny breaks, 2 cm accumulation, alpine winds west 10 to 20 km/h, treeline temperatures around -6 °C.

Friday

Mix of sun and cloud, up to 8 cm accumulation, alpine winds west 5 to 15 km/h, treeline temperatures around -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Remote triggering is a concern, watch out for adjacent and overhead slopes.
Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
Minimize exposure during periods of heavy loading from rain.
Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.