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Avalanche Forecast

Archived

Dec 18th, 2019–Dec 19th, 2019

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

Regions

South Coast Inland.

The barrage of storms hitting the coast is not expected to bring much precipitation inland, but be prepared to choose more conservative terrain if new snow exceeds forecast amounts.

Confidence

Low - Forecast snowfall amounts are uncertain. Recent weather patterns have resulted in a high degree of snowpack variability within the region. Uncertainty is due to the limited number of field observations.

Weather Forecast

WEDNESDAY NIGHT - Cloudy with scattered flurries bringing up to 5 cm of new snow. Moderate to strong southwest winds.

THURSDAY: A mix of sun and cloud with flurries increasing overnight. Light to moderate south winds. Alpine high temperatures around -5.

FRIDAY: Cloudy with 10-15 cm of new snow from the overnight period and scattered flurries bringing another 5-10 cm of new snow. Light south winds. Alpine high temperatures around -3

SATURDAY: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Alpine high temperatures around -6.

Avalanche Summary

Observations are limited in this region, though there was a MIN report of several small human triggered avalanches around the Coquihalla Summit area on Saturday after only 20 cm of new snow had accumulated. Click here to read the report.

By Sunday morning, there was up to 60 cm of new snow in the south of the region. In the absence of new observations, and given the avalanche activity that occurred as we reached 20 cm, it would be wise to choose terrain while assuming a substantial storm slab remains sensitive to human triggering

There have been no avalanches reported in recent days in the northern part of the region. It is expected that reactive new wind slab and/or storm slabs have been forming at higher elevations. Areas that see more new snow from the ongoing series of storms will be the most concerning.

Snowpack Summary

A layer of new snow has begun to accumulate on the surface throughout the region, burying snowpack conditions that vary greatly from north to south within the region.

In the south, near the Coquihalla, up to 60 cm of snow from a storm last weekend likely sits on a weak layer of surface hoar. Avalanches began to be reported on this layer after it was buried only 20 cm deep, however new observations are limited. The middle of the snowpack contains a mix of hard crusts and facet/crust layers. Snowpack depths at treeline are about 100-150 cm.

In the north, near the Duffey Lake area, last week's storm only brought about 10-15 cm of new snow, which has seen significant wind redistribution and is now sitting on an already very thin snowpack. Snowpack depths at treeline are about 40-50 cm.

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.