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

Dec 24th, 2020–Dec 25th, 2020

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

Regions

Purcells.

The load sitting on a variety of buried weak layers has reached a tipping point. If triggered, avalanches running on these weak layers will likely be large and destructive. Continue to choose conservative terrain in the coming days. 

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence. Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

THURSDAY NIGHT: Clear periods, light southwest wind, alpine temperature near -12 C.

FRIDAY: Mix of sun and cloud, light southwest wind, alpine temperature near -7 C.

SATURDAY: Scattered flurries, light west wind, alpine temperature near -7 C.

SUNDAY: Mainly cloudy with sunny breaks, light west wind, alpine temperature near -8 C.

Avalanche Summary

On Wednesday there was a report of a snowmobile triggered size 2 deep persistent slab avalanche in the north of the region. This MIN post highlights the avalanche and the current nature of the snowpack.

On Tuesday there were several reports of deep persistent slab avalanches running size 2-3 on southeast, east and northeast aspects. Three of these were size 2's triggered by skiers. Check out this MIN report from Tuesday afternoon for an example. As well, there were numerous size 1-1.5 explosives controlled storm slab avalanches. 

During the day on Monday reports indicate a few explosives controlled size 1-2 storm slab avalanches in the north of the region.

Snowpack Summary

30 to 75 cm of storm snow fell last week. Winds blowing from a variety of directions have built slabs in lee features at upper elevations, reactive cornices have grown too. 

Below the storm snow, there are a variety of layers of concern. The early December surface hoar is down 30 to 80 cm below the surface now. It recently been sensitive to remote triggering which is well illustrated in this MIN post from the Golden area.

Below, or near the surface hoar you may encounter a crust. This crust can be bound as high as 2400 m in the south of the region and 1800 m in the north.  

The lower snowpack is characterized by more crusts, the most notable is a rain crust from early November that is 50 to 130 cm deep. This crust is sitting near the base of the snowpack, surrounded by a weak layer of sugary facets. It is most likely to be reactive to human triggers or in a step-down from a smaller avalanche in shallow, rocky areas.

Terrain and Travel

  • Uncertainty is best managed through conservative terrain choices at this time.
  • Be aware of the potential for large avalanches due to the presence of buried surface hoar.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.
  • Remote triggering is a concern, watch out for adjacent and overhead slopes.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.