Avalanche Forecast

Archived

Jan 27th, 2024–Jan 28th, 2024

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Purcells, East Purcell, Bull.

Deeply buried weak layers are expected to become active with rising freezing levels.

Choose conservative terrain free of overhead hazards.

Confidence

Moderate

Avalanche Summary

There have been many large (size 2) to very large (size 4) rider-triggered avalanches on deeply buried weak layers in the Purcells this week. Mainly in the alpine but with whumpfing reported below treeline as well.

Snowpack Summary

There are various old surfaces including recent snow settling, wind-affected snow, and sugary facets.

The mid-snowpack has a couple of crusts and is generally faceted and weak above them.

At the base of the snowpack, weak faceted grains and depth hoar are present.

Weather Summary

Saturday Night

Cloudy with a trace of snow, southwest alpine wind 15 to 30 km/h, treeline temperature -2 °C.

Sunday

Mostly cloudy with 5 to 10 cm of snow, southwest alpine wind 20 to 40 km/h, treeline temperature 0 °C, freezing level 2000 m.

Monday

Mostly cloudy with no new snow, southwest alpine wind 30 to 50 km/h, treeline temperature 3 °C, freezing level 2500 m.

Tuesday

Mostly cloudy with a trace of snow, southwest alpine wind 20 to 40 km/h, treeline temperature 3 °C, freezing level 2200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.