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Avalanche Forecast

Archived

Jan 9th, 2024–Jan 10th, 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 unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Purcells, Dogtooth, East Purcell.

A predominantly weak and facetted lower snowpack remains the primary avalanche concern.

Confidence

Moderate

Avalanche Summary

Numerous natural, rider and explosively triggered avalanches have been reported since the end of last week, predominantly small in size (1 and 1.5) and storm or wind slab avalanches.

Of note was a large (size 2.5) avalanche that scrubbed down to basal facets, which occurred over the weekend in very steep alpine terrain, on a northerly aspect.

If you go out in the backcountry, please consider sharing your observations on the Mountain Information Network (MIN).

Snowpack Summary

Approximately 30 cm of new snow over the last week sits atop a shallow and generally weak snowpack.

Several problematic weak layers exist deep within the snowpack. Of greatest concern are weak facets and/or depth hoar located at the bottom of the snowpack, especially in alpine terrain.

Snowpack depths at treeline range from 60 to 150 cm.

Weather Summary

Tuesday Night

Partly cloudy with up to 5 cm of snow, southwest alpine winds 10 to 20 km/h, treeline temperature -10 °C.

Wednesday

Partly cloudy with trace snow amounts, west alpine winds 10 to 20 km/h, treeline temperature -12 °C.

Thursday

Partly cloudy with up to 5 cm of snow, variable alpine winds 10 to 20 km/h, treeline temperature dropping from -15 °C to -25 °C.

Friday

Sunny with no precipitation, north alpine winds 10 to 20 km/h, treeline temperature -32 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Be aware of the potential for surprisingly large avalanches due to deeply buried weak layers.

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.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.