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 5th, 2021–Dec 6th, 2021

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

Regions

South Coast Inland.

Wind slab formation will be of greatest concern in the south of the region, where upwards of 20 cm of low density snow sits on top of a crust. Elsewhere, thinner isolated pockets can still be surprisingly reactive as they are likely poorly bonded to underlying surfaces.

Confidence

Moderate - Uncertainty is due to limitations in the field data. Uncertainty is due to the speed, direction, or duration of the wind and its effect on the snowpack.

Weather Forecast

Sunday night: A trace of new snow. Moderate southwest wind. Treeline temperature around -13.

Monday: Flurries around 5 cm. Light to moderate northwest wind. Treeline high temperatures around -8.

Tuesday: Cloudy with flurries starting in the afternoon. Strong southwest wind. Treeline high temperatures around -3.

Wednesday: New snow 10-20 cm. Strong southwest wind. Treeline high temperatures around -8.

Avalanche Summary

On Saturday, some loose dry sluffing and thin soft slab reactivity were seen in steep terrain and near ridge crests in the neighboring Sea to Sky region. The most recent reports we have from the inland are of explosives producing a size 2 wind slab avalanche in the Hurley on Thursday.

Snowpack Summary

5-20 cm of new low density snow may sit over a widespread layer of small surface hoar crystals which we will continue to monitor going forward. This sits over wind affected snow in the alpine and a thick, supportive crust below 1800 m. Between 1800-2100 meters, this crust exists shallowly buried by wind affected snow. 

A couple of buried weak layers produced large avalanches during a previous storm. Snowpack models and observations in the neighboring Sea to Sky region indicate that these layers have been reset by previous rain at treeline, but uncertainty remains around their status in the alpine. These include a layer of surface hoar down an estimated 90-120 cm and deeper crust/facet combo layer.

Average snowpack depths in the alpine are now likely closer to 150-200 cm. Below treeline, depths of 30-50 cm have been reported around 500 m, decreasing dramatically with elevation, and still below threshold for avalanches in many areas. Early season hazards such as rocks, stumps, and creeks are still a concern below the alpine.

Terrain and Travel

  • Be carefull around freshly wind loaded features.
  • Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
  • Be aware of the potential for loose avalanches in steep terrain where snow hasn't formed a slab.
  • Keep in mind the crust offers an excellent bed surface for avalanches.

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.