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Avalanche Forecast

Archived

Jan 7th, 2025–Jan 8th, 2025

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.
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, Crawford, Dogtooth, East Purcell, Moyie, St. Mary, West Purcell.

Strong west winds will redistribute available snow into fresh wind slabs at upper elevations.

Evaluate terrain carefully for wind slabs before committing.

Confidence

Moderate

Avalanche Summary

As of 4 pm on Tuesday, no new avalanches have been reported in the region.

On Sunday, evidence of several natural persistent slab avalanches triggered by cornice failure was observed up to size 2. See this MIN for details and photos of two of these avalanches.

Avalanche control triggered a size 2 persistent slab avalanche in a treeline feature at 1900 m on a north aspect.

If you head out in the backcountry, let us know what you see by submitting a MIN!

Snowpack Summary

2 to 10 cm of low-density snow sits atop a variety of surfaces, including wind-affected surfaces, surface hoar and facets on northerly aspects and a thin breakable sun crust on southerly aspects. Moderate westerly winds will redistribute available snow into fresh wind slabs at upper elevations.

A weak layer buried in early December can be found down 50 to 90 cm. On shaded slopes, it consists of weak surface hoar or faceted crystals, while on south-facing slopes, it combines a sun crust with facets.

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

Weather Summary

Tuesday Night

Partly cloudy with light flurries, 1 to 2cm. 20 to 40 km/h west ridgetop wind. Treeline temperature -5 °C.

Wednesday

Partly cloudy with light flurries, 1 cm. 15 to 30 km/h northwest ridgetop wind. Treeline temperature -7 °C.

Thursday

A mix of sun and cloud. 15 to 30 km/h northwest ridgetop wind. Treeline temperature -7 °C.

Friday

Mainly cloudy with light flurries, 1 to 4 cm. 20 to 40 km/h southwest ridgetop wind. Treeline temperature -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind-affected terrain.
  • Be careful with wind-loaded pockets, especially near ridge crests and rollovers.
  • Avoid thin areas like rocky outcrops where you're most likely to trigger avalanches on deep weak layers.
  • Seek out sheltered terrain where new snow hasn't been affected by wind.

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.