Avalanche Forecast

Archived

Jan 29th, 2024–Jan 30th, 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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Purcells, Dogtooth, East Purcell, West Purcell, Bull.

A weak, shallow snowpack impacted by rain has created dangerous avalanche conditions.

Avoid overhead exposure, very large natural avalanches have the potential to run to valley bottom.

Confidence

Moderate

Avalanche Summary

Observations have been limited, but there is evidence of a widespread natural avalanche cycle from the past few days as rain impacted the snowpack.

There have been many large to very large (size 2-4) rider-triggered avalanches in the Purcells this week.

If poor riding quality doesn't deter you on Tuesday, keep in mind that human-triggered avalanches remain likely. Avoid overhead exposure, very large natural avalanches have the potential to run to valley bottom.

Snowpack Summary

Rain has created a moist or wet upper snowpack at all elevations. A weak surface crust may have formed overnight at upper elevations.

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

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

Weather Summary

Monday Night

Cloudy with clear periods, no precipitation. Alpine wind southwest 15 to 40 km/h. Treeline temperature drops to 0 °C, freezing level 2000 m.

Tuesday

Cloudy with sunny periods and isolated showers. Alpine wind southwest 15 to 40 km/h. Treeline temperature 0 °C, freezing level 2500 m.

Wednesday

Cloudy with sunny periods and isolated showers. Alpine wind south 20 to 40 km/h. Treeline temperature 0 °C, freezing level 2500 m.

Thursday

A mix of sun and cloud, no precipitation. Alpine wind light from the south. Treeline temperature 0 °C, freezing level 1900 m

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Make conservative terrain choices and avoid overhead hazard.
Be aware of the potential for large, deep avalanches to run full path or even longer.
Avoid steep slopes when air temperatures are warm, or solar radiation is strong.
Keep in mind that wet avalanches can be destructive due to their high density.

Problems

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.