Avalanche Forecast

Issued: Dec 8th, 2017 3:33PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Deep Persistent Slabs and Wind Slabs.

cgarritty, Avalanche Canada

Northwest Inland.

Weaknesses deep in the snowpack will heal much more slowly than wind slabs. Keep your guard up around big overhead terrain and in thin snowpack areas in the alpine.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

Saturday: Mainly cloudy with isolated wet flurries and a trace of new snow to higher elevations. Light to moderate southwest winds. Alpine temperatures hovering around 0 as the temperature inversion persists. Cooler at lower elevations.Sunday: Cloudy with continuing light wet flurries bringing a possible 2 cm of new snow to alpine elevations. Light rain below about 1800 metres. Light to moderate south winds. Freezing level to 2300 metres with alpine temperatures around 0 to +1.Monday: A mix of sun and cloud. Moderate south winds. Freezing level to 3200 metres with alpine temperatures around +5. Cooler at valley bottom due to temperature inversion.

Avalanche Summary

No new avalanches have been reported, however it is expected that warm alpine temperatures and sunshine initiated natural activity on steep solar aspects at higher elevations on Thursday and Friday. Looking forward, expect any new snow accumulations to bond poorly with the crust and surface hoar that form our current snow surface.

Snowpack Summary

Average snowpack depths now total 80-140 cm at treeline elevations and up to 160 cm in the alpine. (Depths of up to 210 cm have been reported from the Howsons.) Solar and temperature crusts are expected to have formed on the wind-affected surface at higher elevations on Thursday. Below the surface, Approximately 30-50 cm of storm snow now overlies two crusts that were buried near the end of November. These crusts are widespread and extend into the alpine. Although snowpack tests have previously shown hard results at these crust interfaces, more recent observations have been limited. Below these crusts, a well settled midpack overlies the late October crust near the base of the snowpack. This "crust/facet combo" layer is widespread and has been reactive to rider and remote triggers. It also continues to produce sudden snowpack test results.

Problems

Deep Persistent Slabs

The late October crust lies near the base of the snowpack with a thin layer of weak, sugary snow above it. This layer should be on a strengthening trend, but a heavy trigger in a thin snowpack area may still be enough to cause it to react.

Be aware of the possibility for full depth avalanches due to deeply buried weak layers.Be especially cautious in shallow snowpack areas where triggering a deeper layer may be easier.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Wind Slabs

Older wind slabs exist on a wide range of aspects. Although they are expected to have become quite stubborn, they may still react to heavy triggers in unsupported terrain.

If triggered, wind slabs may step down to deeper layers and result in large avalanches.Avoid steep convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 9th, 2017 2:00PM