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Avalanche Forecast

Archived

Jan 19th, 2025–Jan 20th, 2025

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.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells, Crawford, Dogtooth, East Purcell, West Purcell.

Seek out wind-sheltered terrain below treeline for the softest snow to ride and lowest hazard.

Use caution in wind-affected terrain and avoid steep, rocky slopes with shallow snow cover.

Confidence

Moderate

Avalanche Summary

Last Thursday and Friday, several size 1-2 wind slab avalanches were reported across the Eastern Purcells.

Looking forward, we suspect wind slabs may remain possible to trigger in isolated areas, especially where they overlie a layer of surface hoar.

Reports have been limited. If you venture into the backcountry, please consider submitting your observations to the MIN.

Snowpack Summary

Recent strong to extreme winds from shifting directions have formed wind slabs of varying thickness on lee slopes. While these slabs are gaining strength, they remain possible to trigger in isolated areas. They may rest on a mix of underlying surfaces, including sun crust, surface hoar, and facets.

A surface hoar layer from early January, buried 20–40 cm, may be reactive to human triggers, particularly where it is covered by a wind slab.

A persistent weak layer of facets buried in early December is on average 60 to 90 cm deep. Near Invermere this layer may only be buried 30 cm. Triggering this layer may be possible in isolated areas.

The snowpack base consists of a thick crust and facets in many areas.

Weather Summary

Sunday Night

Clear. 10 km/h north ridgetop wind. Treeline temperature -22 °C.

Monday

Sunny. 10 km/h west ridgetop wind. Treeline temperature -20 °C, with a possible temperature inversion.

Tuesday

Mostly sunny. 30 to 50 km/h west ridgetop wind. Treeline temperature -16 °C.

Wednesday

Mostly sunny. 10 to 20 km/h west ridgetop wind. Treeline temperature -15 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully evaluate steep lines for wind slabs.
  • Avoid steep, rocky, and wind-affected areas where triggering slabs is more likely.
  • Be aware of the potential for large avalanches due to buried weak layers.
  • Seek out wind sheltered terrain below treeline where you can avoid wind slabs and find great riding.

Problems

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.

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.