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Avalanche Forecast

Archived

Dec 20th, 2023–Dec 21st, 2023

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

Regions

Purcells, Esplanade, Dogtooth, East Purcell, West Purcell.

Use extra caution at higher elevations with shallow snowpack, especially where the buried crust is breakable. A tricky layer of surface hoar is continuing to produce large avalanches.

Confidence

Moderate

Avalanche Summary

On Tuesday, a skier remotely triggered a large size 2.5 avalanche in the Esplanade Range. This persistent slab occurred on a southeast alpine slope and ran on the concerned surface hoar layer 40-60 cm deep. Small loose dry avalanches and skier-triggered wind slabs were also reported on isolated alpine features.

If you go out in the backcountry, please consider sharing your observations on the Mountain Information Network (MIN).

Snowpack Summary

The region received up to 10 new snow recently, bringing the total of fresh snow to 20-30 cm. Moderate to strong westerly winds have redistributed into deep pockets in lees. This overlies a variety of surfaces including a surface hoar layer, sun crust, and wind-affected snow.

A prominent rain crust is found 40 to 60 cm deep and has been reported to extend as high as 2300 m around Invermere and 2000 m around Golden. A layer of surface hoar is also found at this depth and is a particular concern in areas without a thick crust.

The lower snowpack contains large, weak snow grains and in some places a hard crust near the ground. Typical snowpack depths at treeline are 60 to 110 cm, and taper rapidly below treeline.

Weather Summary

Wednesday Night

Cloudy with isolated flurries, trace accumulation, alpine wind southwest 30 to 40 km/h, treeline temperature -3 °C, freezing level at 1500 m.

Thursday

Cloudy with isolated flurries, trace accumulation, alpine wind southwest 30 to 40 km/h, treeline temperature -3 °C, freezing level at 1700 m.

Friday

Cloudy, light snow up to 5 cm, alpine wind southwest 40 to 50 km/h, treeline temperature -3 °C, freezing level at 1700 m.

Saturday

Mix of sun and clouds, no precipitation, alpine wind northwest 30 to 40 km/h, treeline temperature -6° C, freezing level at 800 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

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.