Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 19th, 2023–Dec 20th, 2023

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

Regions

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

A buried surface hoar layer remains the primary concern. As you gain elevation, assess continually the conditions. Read our Forecasters' Blog for details of the persistent slab problem.

Confidence

Moderate

Avalanche Summary

On Monday, a large size 2.5 natural avalanche was observed at 2400 m, in the Esplanade Range. The persistent slab triggered a sympathetic avalanche on a slope nearby.

On Sunday, groups triggered persistent slab avalanches (size 2 and size 2.5) on Balu Peak, Glacier National Park. They occurred above 2200 m and are suspected to have failed on a buried surface hoar layer. Although they occurred in neighboring region, this weak layer remains a concern throughout both regions.

Snowpack Summary

10 to 25 cm of recent snow has been redistributed by strong westerly winds 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 30 to 50 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

Tuesday Night

Cloudy with isolated flurries, trace accumulation, alpine wind southwest 30 to 40 km/h, treeline temperature -4 °C, freezing level at1500 m.

Wednesday

Cloudy with isolated flurries, trace accumulation, alpine wind southwest 40 to 50 km/h, treeline temperature -3 °C, freezing level at 1800 m.

Thursday

Cloudy with isolated flurries, trace accumulation, alpine wind southwest 40 to 50 km/h, treeline temperature -3 °C, freezing level at 1700 m.

Friday

Cloudy, light snow 5 cm, alpine wind southwest 40 to 50 km/h, treeline temperature -3 °C.

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.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.

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.