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Avalanche Forecast

Archived

Jan 22nd, 2024–Jan 23rd, 2024

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

Regions

Purcells, Dogtooth, East Purcell, West Purcell.

Avalanche danger may be decreasing, however, the consequences of triggering any avalanche could be severe due to a persistent weakness deep within the snowpack.

Confidence

Moderate

Avalanche Summary

Several explosive-triggered storm and wind slab avalanches were reported over the weekend up to size 2, on a variety of aspects and elevations.

Last week a few explosive-triggered deep persistent slab avalanches (size 2.5 to 3.5) were reported, all in the northwest of the forecast region. These avalanches occurred in areas characterized by generally deeper snowpacks compared to most other areas. All avalanches took place in north-facing alpine terrain.

Snowpack Summary

The upper snowpack continues to settle with mild temperatures. In wind-exposed terrain at treeline and above, recent snow has potentially been redistributed into deeper pockets of wind slabs by predominantly southwest winds.

A layer of faceted snow exists down approximately 30 to 40 cm, created during the extreme cold earlier this month.

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

Weather Summary

Monday Night

Mostly cloudy with 0 to 5 cm of snow, southwest alpine winds 20 to 30 km/h, treeline temperature -4 °C.

Tuesday

Mostly cloudy with trace snow amounts, west alpine winds 20 to 30 km/h, treeline temperature -5 °C.

Wednesday

Mix of sun and cloud with trace snow amounts, southwest alpine winds 20 to 40 km/h, treeline temperature -7 °C.

Thursday

Mix of sun and cloud with trace snow amounts, west alpine winds 20 to 30 km/h, treeline temperature -5 °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.
  • Conditions may have improved, but be mindful that deep instabilities are still present.

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.