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Avalanche Forecast

Archived

Jan 1st, 2024–Jan 2nd, 2024

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

Regions

Purcells, East Purcell, West Purcell.

Be mindful of buried weak layers within range of human triggering.

Confidence

Moderate

Avalanche Summary

Small loose wet avalanches were reported on south aspects in the warm weather on Saturday.

Prior to the weekend, explosive-triggered wind slabs were reported to size 1.5 in the northwest Purcells and ski cuts produced loose dry to size 1 in the upper snowpack facets near Invermere.

Snowpack Summary

Various snow surfaces exist including crusts, settled powder, unconsolidated facets and old wind slab. Beneath lies a complex snowpack with many layers that vary across the region.

The most prominent is a layer of surface hoar buried 20-50 cm deep. It is less of a concern in areas where a strong, supportive crust exists above the surface hoar layer.

The lower snowpack is typically characterized by sugary, facetted crystals and a crust.

Snowpack depths at treeline average 50-120 cm with significant variability across the region.

Weather Summary

Monday night

Partly cloudy, ridgetop wind 15 km/h southeast, treeline temperature -10 °C.

Tuesday

A mix of sun and cloud, ridgetop wind 15 km/h south, treeline temperature -7 °C.

Wednesday

Mostly cloudy, ridgetop wind <10 km/h south, treeline temperature -6 °C.

Thursday

A mix of sun and cloud, ridgetop wind <10 km/h south, treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Use caution on large alpine slopes, especially around thin areas that may propagate to deeper instabilities.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.