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Avalanche Forecast

Archived

Dec 15th, 2019–Dec 16th, 2019

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

Regions

Sea To Sky.

Conservative terrain selection is a good management strategy for a persistent slab problem, as avalanches are typically difficult to predict in these conditions.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

SUNDAY NIGHT - Mainly cloudy with isolated flurries / southwest wind, 20-30 km/h / alpine low temperature near -10

MONDAY - Flurries, 5-10 cm / southwest wind, 30-60 km/h / alpine high temperature near -5

TUESDAY - Snow, 10-20 cm / southwest wind, 40-70 km/h / alpine high temperature near -3 / freezing level 1200 m

WEDNESDAY - Snow, 10-15 cm / southwest wind, 40-60 km/h / alpine high temperature near -4 / freezing level 800 m

Avalanche Summary

There were a few persistent slab avalanches reported on Saturday, both natural and human triggered, up to size 2.5. Click here to check out a MIN report of a persistent slab avalanche in the Whistler backcountry on Saturday.

On Friday, there were several reports of natural, human and explosives triggered avalanches up to size 2. The majority of these avalanches released on the persistent weak layer that was buried in mid November.

On Thursday, there were several reports of human and explosives triggered avalanches up to size 2. Some of these avalanches stepped down to the persistent weak layer that was buried in mid November.

Snowpack Summary

15-25 cm of recent fresh snow likely sits on a weak layer of surface hoar in some areas, as well as sugary faceted snow.

There is a persistent weak layer from mid November that consists of a crust/facet combination, that is now down approximately 35-70 cm. This layer has been responsible for several recent avalanches. Snowpack tests consistently indicate that this layer can be triggered by humans and propagate widely, resulting in large avalanches.

The snowpack is unusually shallow and weak for the Sea to Sky region. Snowpack depths range between 80-200 cm and taper quickly at lower elevations.

Problems

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.