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Avalanche Forecast

Archived

Jan 4th, 2025–Jan 5th, 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, human triggered possible.
Treeline
Natural avalanches unlikely.
Below Treeline
Natural avalanches unlikely.

Regions

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

There is still uncertainty about the reactivity of deeper weak layers.

Steer clear of rocky, thin, and shallow areas where triggering is possible.

Confidence

Moderate

Avalanche Summary

Explosive testing on both Tuesday and Wednesday triggered many small ( size 1 to 1.5 ) windslab avalanches. These all occurred between 2000 and 2500 meters.

On Monday, a rider accidentally triggered a small avalanche from a shallow alpine slope on Repeater Peak near Golden, getting carried through cliff features and a gully. The failure plane is suspected to be the persistent weak layer down 60 cm. Read the MIN report here.

Snowpack Summary

In sheltered areas, 20 to 75 cm of settled snow is present. Previous southwest winds have redistributed this snow, creating deeper deposits on leeward slopes at higher elevations. The surface snow varies, with surface hoar and facets on northerly slopes and a thin, breakable sun crust on southerly slopes.

A weak layer buried in early December can be found down 40 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.

Read this MIN report for updated conditions in the southern section of this forecast region.

Weather Summary

Saturday Night

Partly cloudy with isolated flurries 1 cm. 5 to 10 km/h south ridgetop wind. Treeline temperature -9 °C.

Sunday

Partly cloudy, with light snowfall 1 to 2 cm. 5 to 10 km/h northwest ridgetop wind. Treeline temperature -4 °C.

Monday

Partly cloudy, with afternoon clearing . 10 to 15 km/h northwest ridgetop wind. Treeline temperature -8 °C.

Tuesday

Mostly clear. 5 to 10 km/h southwest ridgetop wind. Treeline temperature -9 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Loose avalanches may step down to deeper layers, resulting in larger avalanches.

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.