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Avalanche Forecast

Archived

Jan 23rd, 2023–Jan 24th, 2023

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

Regions

Lizard-Flathead, South Rockies, Flathead, Lizard, Bull, Elkford East, Elkford West.

Be mindful of wind slabs and overhead hazards as you transition into exposed terrain.

The complex snowpack continues to demand thoughtful terrain selection to avoid triggering a very large avalanche.

Confidence

Moderate

Avalanche Summary

Sunday saw a cornice fail naturally but it did not trigger buried weak layers in this instance. Be aware of what is above you as you travel through the terrain.

Although they have not produced avalanches in the last few days, instabilities from the deep persistent slab still exist and should be assumed to be lurking in the backcountry.

Snowpack Summary

Soft thin wind slabs have developed in exposed areas. It has been blending into older wind-affected surfaces above 1800 to 2000 m. Below this elevation, recent snow has settled on a melt-freeze crust that developed earlier this month.

A crust/facet layer, 2 to 15 cm thick at treeline is 50 to 90 cm below the surface. Where it's thickest, it caps the settled and consolidated mid-snowpack.

Another crust/facet layer is down 70 to 150 cm. Below this crust, the basal snowpack is weak and faceted. The total snowpack depth ranges between 120 and 250 cm.

Weather Summary

Monday Night

Cloudy, trace accumulation, wind southwest 27 km/h, treeline temperatures -10 C.

Tuesday

Cloudy with sunny breaks, trace accumulation, wind west 22 km/h increasing later in the day, treeline temperatures -8 C with freezing level rising to 1000 m.

Wednesday

Cloudy with increasing sunny periods later in the day, potential trace accumulation, wind west 15 km/h, treeline temperatures -5 C.

Thursday

Mostly cloudy, trace accumulation, wind west 17 km/h, treeline temperature -4 to 0 C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid thin areas like rock outcroppings where you're most likely to trigger avalanches failing on deep weak layers.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • Avoid exposure to slopes that have cornices overhead.

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.