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Avalanche Forecast

Archived

Feb 1st, 2024–Feb 2nd, 2024

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

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

Keep an eye on the snow surface as you travel through the mountains.

When the snow surface is wet or moist avalanches will be more likely.

Confidence

Moderate

Avalanche Summary

The natural avalanche cycle observed on the weekend and earlier in the week, due to the warming event, has slowed down. However there were still reports of a few wet slab or persistent slab avalanches to size 2-2.5 being reported Tuesday and Wednesday.

Until the snowpack gets re-frozen by cold temperatures, human-triggered avalanches remain possible.

Snowpack Summary

A new surface crust exists at treeline extending up to mountain tops  or near mountain tops, This crust will likely break down during the day at treeline. Below treeline the snow surface is wet or moist.

The top 50 cm at treeline is moist  with several layers of crusts and facets below.

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

Weather Summary

Thursday Night

A mix of cloud and clear skies with trace amounts of new snow, southeast alpine wind 10 to 25 km/h, freezing level falling to 1300 m.

Friday

Mostly cloudy with up to 5 cm of new snow expected in the alpine, southwest alpine wind 10 to 20 km/h, freezing level rising to 2100 m.

Saturday

Cloudy with 5 to 15 cm of new snow expected,  northeast alpine wind 15 to 25 km/h, treeline temperature -4°C.

Sunday

Mostly cloudy with up to 10 cm of new snow expected, variable alpine winds 10 to 15 km/h, treeline temperature -6°C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Keep in mind that human triggering potential persists as natural avalanching tapers off.
  • 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.
  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.