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Avalanche Forecast

Archived

Jan 11th, 2024–Jan 12th, 2024

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

Regions

Purcells, Dogtooth, East Purcell.

Watch for thin wind slabs in alpine terrain.

Extreme cold significantly increases the consequences of an incident in the backcountry.

Confidence

Moderate

Avalanche Summary

Several storm and wind slab avalanches were reported across the region on Tuesday and Wednesday. They occurred on a variety of aspects and elevations and were both naturally and explosive triggered, up to size 2.

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

Snowpack Summary

Up to 40 cm of recent, low-density snow sits atop a variety of old surfaces, including surface hoar, crusts and/or facets.

The mid and lower snowpack is generally weak with several layers of note. Of greatest concern are weak facets and/or depth hoar located at the bottom of the snowpack, particularly in alpine terrain.

Snowpack depths at treeline range from 60 to 150 cm.

Weather Summary

Thursday Night

Mostly clear with no precipitation, north alpine winds 10 to 20 km/h, treeline temperature -35 °C.

Friday

Sunny with no precipitation, northwest alpine winds 10 to 30 km/h, treeline temperature -32 °C.

Saturday

Sunny with no precipitation, northwest alpine winds 10 to 30 km/h, treeline temperature -30 °C.

Sunday

Sunny with no precipitation, north alpine winds 10 to 20 km/h, treeline temperature -26 °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

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.

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.