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Avalanche Forecast

Archived

Apr 3rd, 2023–Apr 4th, 2023

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, human triggered possible.
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, Dogtooth, East Purcell, West Purcell.

Carefully assess for changing conditions - unstable, spring weather can deliver highly variable snow amounts or periods of strong sun, which can increase avalanche hazard locally.

Confidence

Moderate

Avalanche Summary

On Sunday a size 3 naturally triggered, deep persistent slab avalanche was reported in the western Purcells (southwest of Panorama). It occurred in large alpine terrain, west facing at 2800 m.

On Friday a size 3 naturally triggered avalanche was reported in the Dogtooth Range. While the failure plane is unknown the report mentions impressive propagation.

Snowpack Summary

Recent snow and wind have formed wind slabs at upper elevations. Surface hoar may exist below the recent snow, in wind-sheltered and shaded terrain.

The mid-snowpack may still contain a few persistent weak layers of surface hoar in sheltered treeline terrain. No recent avalanche activity has occurred on these layers suggesting the layers have gained strength.

The lower snowpack includes a widespread layer of large, weak facets and or depth hoar crystals. This weak layer continues to be responsible for several very large and destructive avalanches throughout the season.

Weather Summary

Monday night

Mostly cloudy with clear breaks. Light east ridgetop wind. Alpine temperatures -5 to -10 C. Freezing level at valley bottom.

Tuesday

Mostly cloudy with sunny breaks and scattered flurries, with trace accumulation. Light east ridgetop wind. Alpine temperatures -5 to -10 C. Freezing level 1500 m.

Wednesday

Mix of sun and cloud. Light southwest ridgetop wind. Alpine temperatures -5 to -10 C. Freezing level 1500 m.

Thursday

Mix of sun and cloud. Light to moderate southwest ridgetop wind. Alpine temperatures -5 to -10 C. Freezing level 1200 m.

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.
  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

Problems

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.

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.