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 7th, 2021–Dec 8th, 2021

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

South Coast Inland.

New snow and wind will form fresh wind slabs at upper elevations. These may be especially reactive where they sit over a weak layer or a crust.

Confidence

Low - Uncertainty is due to the limited number of field observations. Uncertainties in both the snowpack structure and the weather forecast limit our confidence.

Weather Forecast

Greatest snowfall amounts for Tuesday will be concentrated near Hope.

Tuesday night: New snow 5-10 cm. Strong southwest wind. Freezing level 800 m.

Wednesday: New snow 5-10 cm. Moderate southwest wind. Treeline high temperature around -8. Freezing level dropping to valley bottom.

Thursday: New snow 5-10 cm. Light westerly wind. Treeline high temperatures around -12.

Friday: Flurries up to 5 cm. Moderate southwest wind. Treeline high temperatures around -9.

Avalanche Summary

Over the weekend, 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 last Thursday.

Snowpack Summary

10-20 cm of new snow falls over wind affected surfaces and/or a crust.

The south, having endured warmer temperatures and more rainfall, is largely below threshold for avalanches at most elevations. Previous snow has seen extensive wind effect, scouring the rain crust clean in some areas, while piling up to 40 cm over it in others.

In the north, the new snow may be sitting over a layer of surface hoar crystals, older wind affected snow in the alpine, a thick crust below 1800 m or a combination of these.

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.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Make observations and assess conditions continually as you travel.
  • Closely monitor how the new snow is bonding to the old surface.
  • 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.