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Avalanche Forecast

Archived

Apr 5th, 2023–Apr 6th, 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.

Continually assess your local conditions. Periods of intense sun can quickly destabilize the surface snow.

Confidence

Moderate

Avalanche Summary

A few skier-triggered storm or wind slab avalanches were triggered on Tuesday. All were relatively thin (10 -20 cm), occurring along exposed ridge features in the western Purcells.

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

Dry, powder snow remains on shaded (northerly) slopes. While moist snow or thin crusts exist on most solar slopes at all elevations.

The mid-snowpack may still contain a number of weak layers, primarily in sheltered treeline terrain. However, no recent avalanche activity has occurred on these layers suggesting the layers are likely no longer a primary concern.

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

Wednesday night

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

Thursday

Mix of sun and cloud. Light southwest ridgetop wind. Alpine temperatures 0 to -5 C. Freezing level 2000 m.

Friday

Mostly cloudy, with scattered flurries and trace accumulation. Light to moderate southwest ridgetop wind. Alpine temperatures 0 to -5 C. Freezing level 2100 m.

Saturday

Mostly cloudy, with scattered flurries and trace accumulation. Light to moderate southwest ridgetop wind. Alpine temperatures 0 to -5 C. Freezing level 1900 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • 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.