Avalanche Forecast

Archived

Feb 4th, 2024–Feb 5th, 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, Bull.

A bit of new snow and wind has formed fresh wind slabs at upper elevations. The cooler weather has helped to stabilize the snowpack, however we continue to be wary of deeply buried weak layers.

Confidence

Moderate

Avalanche Summary

There is now new avalanche activity to report.

Snowpack Summary

5-10 cm of new snow has accumulated over a crust that varies in thickness and elevation throughout the forecast area. In the Dogtooth Range, this crust thins in the alpine and becomes breakable.

Below the fresh snow and mentioned crust, there is around 50 cm of moist snow with multiple crust and facet layers beneath. The base contains weak faceted grains and depth hoar, which will be continue to be monitored for reactivity.

Weather Summary

Sunday Night

Mostly cloudy with 2 - 5 cm of new snow. Freezing level at valley bottom. Treeline temperature -6 °C. Southeast wind 10-20 km/h.

Monday

Mostly cloudy. Freezing level at valley bottom. Treeline temperature -5 °C. Southeast wind 10 - 20 km/h.

Tuesday

Mostly cloudy with isolated flurries. Freezing level 1300 m, treeline temperature -2 °C South and southwest wind15 - 30 km/h.

Wednesday

Mostly cloudy with flurries. Freezing level 1200 m, treeline temperature -2 °C South wind15 - 30 km/h.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
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.

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.