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Avalanche Forecast

Archived

Jan 2nd, 2024–Jan 3rd, 2024

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

Regions

Dogtooth.

Conservative terrain choices will be your best tool to work the problem of uncertainty around buried weak layers.

Confidence

Moderate

Avalanche Summary

On Sunday, a skier was uninjured after accidentally triggering a size 2 deep persistent slab on basal facets over a smooth rock slab.

Ongoing explosive control work in recent days has consistently produced deep persistent slab avalanches, size 1.5 to 2.

Snowpack Summary

Small amounts of new snow rests on old surfaces including surface hoar, facets, and crusts. Beneath lies a complex snowpack with several layers of concern.

The most prominent is a layer of surface hoar buried 20 to 50 cm deep. It is less of a concern in areas where a strong, supportive crust exists above this layer.

The mid to lower snowpack is typically characterized by sugary, facetted crystals and a basal crust.

Snowpack depths at treeline range from 50 to 130 cm.

Check out this blog post for some insight into the current shallow yet complex snowpack.

Weather Summary

Tuesday Night

Mostly clear with some clouds, potential trace accumulation, ridgetop winds south 15 km/h, treeline temperature -7 °C.

Wednesday

Mix of sun and clouds, trace accumulation, ridgetop winds south 20 km/h, treeline temperature -6 °C.

Thursday

A mix of sun and cloud, 2 cm accumulation, ridgetop winds south-southwest 15 km/h, treeline temperature -7 °C.

Friday

Cloudy with late-day clearing, 2 cm accumulation, ridgetop winds southwest 10 km/h, treeline temperatures -8 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.
  • Be mindful that deep instabilities are still present and have produced recent large 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.

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.