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Avalanche Forecast

Archived

Jan 1st, 2024–Jan 2nd, 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.

Uncertainty around buried weak layers is best managed through conservative terrain choices. Check out this blog post for some insight into the current shallow yet complex snowpack.

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 1.5-2.

Snowpack Summary

A skiff of new snow rests on old surfaces including surface hoar, facets and crusts. Beneath lies a complex snowpack with several layers on our radar.

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

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

Snowpack depths at treeline range from 50-130 cm.

Weather Summary

Monday night

Partly cloudy, ridgetop wind 15 km/h southeast, treeline temperature -10 °C.

Tuesday

A mix of sun and cloud, ridgetop wind 15 km/h south, treeline temperature -7 °C.

Wednesday

Mostly cloudy, ridgetop wind <10 km/h south, treeline temperature -6 °C.

Thursday

A mix of sun and cloud, ridgetop wind <10 km/h south, treeline temperature -5 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

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

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.