Avalanche Forecast

Archived

Feb 9th, 2020–Feb 10th, 2020

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

Cariboos.

Broken skies with little precipitation along with winds switching direction will keep wind slabs at upper elevations the main concern.

Confidence

High - Confidence is due to a stable weather pattern with little change expected.

Weather Forecast

Sunday Night: Cloudy with clear periods. Light to moderate northwest wind. Alpine high temperatures around -10.

Monday: Cloudy with sunny breaks. Light to moderate northwest and west wind. Alpine high temperatures around -7.

Tuesday: Scattered flurries. Light to moderate west wind. Alpine high temperatures around -6.

Wednesday: Mix of sun and cloud. Light to moderate west wind. Alpine high temperatures around -10.

Avalanche Summary

There was a report of a remotely triggered (from a distance) size 2.5 deep persistent slab avalanche. It was 130 cm deep and triggered in a shallow area at 2300 m on a east aspect.

Reports of new avalanche activity Wednesday through Friday were limited to small (size 1-1.5) skier or rider triggered wind slabs along steep ridgetop features.

Reports from Wednesday included three very large (size 3) persistent slab avalanches in the southeastern part of the region, not far from Allan Creek. These avalanches failed naturally on the 150 cm-deep late December surface hoar described in our snowpack summary. They occurred on north and east aspects at around 2300 metres.

Snowpack Summary

20-60 cm of snow from the last week overlies previously wind-affected snow at higher elevations, with diminished depths of about 20-30 cm above a widespread melt-freeze or rain crust up to about 1700 metres.

The mid and lower snowpack are generally well settled, however an aging weak layer of surface hoar from late December, currently buried 70 to 150 cm deep, has shown surprisingly long-lived instability on slopes between 1700-2400 m (above the crust elevation and below the most wind-affected elevations), warranting increased caution around steeper slopes in this elevation band, particularly in the southern half of the region.

Terrain and Travel

Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.
Be alert to conditions that change with elevation and sun exposure.
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.