Avalanche Forecast

Archived

Feb 5th, 2021–Feb 6th, 2021

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

South Coast.

Reactive wind slabs may exist at upper elevations. The persistent weak layer may still be possible to trigger in areas around treeline that have not already avalanched.

Confidence

Moderate - Uncertainty is due to limitations in the field data.

Weather Forecast

Friday night: Mostly cloudy, moderate northwest ridgetop wind, treeline temperature -1, freezing level 1000 m.

Saturday: Light flurries, up to 5 cm, strong northwest ridgetop wind, treeline high -1, freezing level 1000 m.

Sunday: Mix of sun and cloud, light westerly ridgetop wind, treeline high -5, freezing level 500 m.

Monday: Mix of sun and cloud, light northwest ridgetop wind, treeline high -7, freezing level 300 m.

Avalanche Summary

Human triggered storm slab avalanches remain likely in wind loaded areas at upper elevations. The recently buried persistent weak layer may be possible to trigger in areas that have not already avalanched.

It was a busy week for avalanche activity in the South Coast mountains, with natural and/or human triggered avalanches reported every day between Monday, January 25, and Monday, February 1, culminating in a widespread natural avalanche cycle, with avalanches up to size 3, on Monday night. Most of these avalanches failed on the persistent weak layer. This was likely the peak of the avalanche activity associated with this layer.

North Shore Rescue responded to a serious, but non-fatal avalanche incident last Tuesday evening near Cypress Mountain Resort. One person was involved and was partially buried. The avalanche was a size 2 storm slab on a west aspect at approximately 1100 m and failed on the persistent weak layer.

Snowpack Summary

100-150 cm of snow sits over a widespread persistent weak layer. This weak layer consists of a crust that also has weak facets and surface hoar on top of it in many areas. Although very much still present, low elevationsrain crusts and dense snow closer to the surface have a bridging effect over this layer, making it more difficult to trigger.

Click here to watch North Shore Rescue's snowpack conditions update from Friday.

Terrain and Travel

Be careful as you transition into wind affected terrain.
Conditions may have improved, but be mindful that deep instabilities are still present.

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.