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Avalanche Forecast

Archived

Mar 23rd, 2025–Mar 24th, 2025

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

Regions

Purcells, Dogtooth, East Purcell.

Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.

Confidence

Moderate

Avalanche Summary

On Friday and Saturday, natural wind slab avalanches up to size 2 were reported near Invermere, including one which stepped down to a persistent weak layer. Last week, numerous persistent slab avalanches were reported in the central Purcells, including remote triggers from 60 m away.

Snowpack Summary

New snow falls over wind slabs at upper elevations, while rain wets the surface below 2000 m.

An interface from early March, 30 to 50 cm deep, consists of a crust on sunny slopes and lower elevations, and surface hoar or facets in sheltered, shaded upper elevations.

Persistent weak layers from February and January, including crusts, facets, and surface hoar, are buried 50 to 100 cm deep and remain a concern.

The bottom of the snowpack is composed of large facets, which are becoming reactive again, with some very large avalanches recently failing on this layer.

Weather Summary

Sunday night

Cloudy with 2 to 8 cm of snow. 30 to 40 km/h southwest ridgetop wind. Treeline temperature -1 °C. Freezing level rising to 2100 m.

Monday

Cloudy with 5 to 10 cm of snow above 2000 m and rain below. 20 to 40 km/h southwest ridgetop winds. Treeline temperature 0 °C. Freezing level 2200 m.

Tuesday

Cloudy with 2 to 5 mm of rain. 20 km/h southwest ridgetop winds. Treeline temperature +4 °C. Freezing level 2500 m.

Wednesday

Sunny. 10 to 20 km/h southeast ridgetop winds. Treeline temperature +6 °C. Freezing level 3000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
  • Avoid areas with a thin or variable snowpack.
  • Be aware of the potential for large, destructive avalanches due to deeply buried 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.