Avalanche Forecast

Archived

Dec 27th, 2023–Dec 28th, 2023

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

Purcells, Esplanade, Crawford, Dogtooth, East Purcell, St. Mary, West Purcell.

A complex snowpack exists, with multiple layers of concern that may vary across different locations.

Confidence

Moderate

Avalanche Summary

On Monday, a size 1, skier-triggered persistent slab avalanche was reported in the Crawford area. It occurred on a northwest aspect at treeline.

There have been numerous natural and skier-triggered very large (up to size 3) persistent slab avalanches reported on all aspects at treeline and above in the Esplanade range over the past week. They've occurred on a layer of surface hoar down 50-70 cm.

Snowpack Summary

The upper snowpack continues to settle with mild temperatures and minimal wind.

A layer of buried surface hoar is down roughly 50 to 70 cm and remains concerning in much of the region. It is less of a concern in areas where a strong, supportive crust exists above the surface hoar layer.

As you move south in the region, weak facets near the ground are a concern. Especially in shallow, rocky areas in alpine terrain.

Average snowpack depths at treeline are 70-120 cm which tapers rapidly below treeline.

Weather Summary

Wednesday Night

Cloud building overnight with no precipitation, south alpine winds 0 to 20 km/h, treeline temperature -8 °C.

Thursday

Mostly cloudy with no precipitation, southwest alpine winds 0 to 20 km/h, treeline temperature -6 °C.

Friday

Mix of sun and cloud with no precipitation, southeast alpine winds 0 to 20 km/h, treeline temperature -6 °C.

Saturday

Mix of sun and cloud with no precipitation, southeast alpine winds 0 to 20 km/h, treeline temperature -4 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

In times of uncertainty conservative terrain choices are our best defense.
Avoid shallow snowpack areas, rock outcroppings and steep convex terrain where triggering is most likely.

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.