Avalanche Forecast

Archived

Jan 4th, 2024–Jan 5th, 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 about buried weak layers warrants conservative terrain choices.

Confidence

Moderate

Avalanche Summary

Deep persistent slab avalanches (size 1.5 to 2) have been continually triggered with explosive control over the past week, with the most recent occurrence on Monday. On Sunday, a skier in the Dogtooth Range was uninjured after accidentally triggering a size 2 deep persistent slab on basal facets over a smooth rock slab.

Snowpack Summary

New snow is (very) gradually accumulating over surface hoar, facets, and crusts. Beneath lies a thin and complex snowpack with several layers of concern:

A layer of surface hoar buried 20 to 50 cm deep is a concern in areas where it is not covered by a thick crust.
Weak basal facets near the bottom of the snowpack, especially in alpine terrain.

Read this blog post for more details.

Snowpack depths at treeline range from 50 to 130 cm.

Weather Summary

Thursday night

Mostly cloudy with a trace of snow, alpine wind southwest 20 km/h, treeline temperature -10 °C.

Friday

Mostly cloudy, alpine wind west 20 km/h, treeline temperature -6 °C.

Saturday

Cloudy with 3 to 8 cm of snow, alpine wind southwest 10 km/h, treeline temperature -6 °C.

Sunday

Sunny, alpine wind southwest 15 km/h, treeline temperature -10 °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.
Be mindful that deep instabilities are still present and have produced recent large avalanches.
Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

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.

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.