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Avalanche Forecast

Archived

Mar 26th, 2025–Mar 27th, 2025

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

Regions

Purcells, Dogtooth, East Purcell.

Dangerous avalanche conditions continue, with large, destructive natural avalanches remaining possible.

Confidence

Moderate

Avalanche Summary

Numerous natural, persistent, and deep persistent slab avalanche activity on Wednesday. Wet loose and wet slab activity was widespread throughout the region.

Snowpack Summary

A mix of 5 to 7 cm snow, moist surfaces, and thin, breakable crusts, depending on freezing levels and timing of incoming cooler temperatures and precipitation. Below lies a complex snowpack with several weak layers:

  • 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 showing signs of becoming reactive again, with some very large avalanches recently failing on this layer.

Weather Summary

Wednesday Night

Cloudy, 5 to 7 cm snow, 10 to 20 km/h south ridgetop wind. Treeline temperature 0 °C. Freezing level 2200 m.

Thursday

Mostly cloudy, mixed rain and snow, 3 to 5 cm. 20 to 30 km/h southwest ridgetop wind. Treeline temperature 0 °C. Freezing level 2000 m.

Friday

Mostly cloudy with scattered flurries, 4 to 6 cm. 10 to 20 km/h southeast ridgetop wind. Treeline temperature -2 °C. Freezing level 1500 to 2000 m.

Saturday

Mostly cloudy, scattered flurries 3 to 5 cm. 10 to 15 km/h southwest wind. Treeline temperature 0 °C. Freezing level 1700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Cornice failures could trigger large and destructive avalanches.
  • Avoid exposure to overhead avalanche terrain; avalanches may run surprisingly far.

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.