Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Jan 17th, 2022–Jan 18th, 2022

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.

Be mindful that reactive wind slabs and deep instabilities are still present. Choose well-supported, low consequence slopes.

Confidence

Moderate - Uncertainty is due to field data and reports showing a wide variation in conditions throughout the region.

Weather Forecast

MONDAY NIGHT: Snow 5 cm, moderate westerly wind, treeline temperatures around -3 C, freezing level lowering to valley bottom.

TUESDAY: Flurries then clearing, moderate northwest wind, treeline temperatures around -6 C, freezing level at valley bottom.

WEDNESDAY: Sunny periods, light north wind, treeline temperatures around -10 C, freezing level at valley bottom.

THURSDAY: Light snow, light southwest wind, treeline temperatures around -6 C, freezing level rising to 1000 m.

Avalanche Summary

Fresh wind slabs have been reactive to riders in the last 24 hours, but with limited propagation. Developing cornices were also observed in the western part of the region.

Over the last three days, the early December persistent weak layer has produced few large natural avalanches (2-2.5) in the center of the region. Explosive controls have also produced few size 2 avalanches that failed on the same persistent weak layer, one being remotely triggered. These occurred on thin to thick features on northeast-facing slopes from between 1600 m and 2000 m, where the layer was buried 100 cm + deep. Although avalanche activity has tapper off, it remains a concern across the region.

A natural cycle occurred Thursday releasing several large natural avalanches (size 2.5): storm slabs in alpine terrain, cornice falls pulling storm slabs, wind slabs, and wet slabs running to valley bottom. Smaller loose avalanches were also triggered by solar input and warm temperatures at lower elevations.

Snowpack Summary

Wind and recent dry snow have created reactive wind slabs on alpine lee slopes and open areas at treeline. Around 1900 m and below, a crust is now capping the dense 10-30 cm of snow which has settled significantly with the past mild temperatures. The crust varies from thin/breakable to thick/supportive, according to the aspects and elevation. Below the recent snow, a layer of feathery surface hoar and melt-freeze crusts are found, which seems to be still reactive in isolated areas. Lower elevations have gone through a melt-freeze cycle.

The most notable layer of concern in the snowpack is a crust that was formed in early December and is now down 90-160 cm. Activity on this layer has been sporadic but has generally been triggered on steep, rocky slopes, with a shallow or thin-to-thick snowpack.

Terrain and Travel

  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.