Avalanche Forecast

Issued: Dec 18th, 2014 8:29AM

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

triley, Avalanche Canada

South Coast.

Avalanche danger is increasing as the new storm moves in from the Southwest.

Summary

Confidence

Fair - Freezing levels are uncertain

Weather Forecast

Light snow (5-10 cm) overnight combined with moderate Southeast winds and freezing levels around 1000 metres elevation. Flurries with periods of light snow during the day on Friday combined with moderate to strong Southwest winds. Freezing levels expected to rise up to about 1400 metres on Friday. Light snow (3-8 cm) by Saturday morning and continued snowfall (10-15 cm) during the day Saturday as freezing levels continue to rise and Southwest winds increase to strong-very strong. Freezing levels are forecast to spike up to about 2000 metres by Sunday morning combined with 10-20 mm of precipitation and very strong Southwest winds. This may be rain up into the alpine.

Avalanche Summary

No new reports of avalanches. Expect new storm slab avalanches to increase as the new storm develops.

Snowpack Summary

The new storm is expected to develop a storm slab above the mix of old surface forms that include hard crusts, near surface facets, and surface hoar. Conditions in the Coquihalla area are quite different to the Duffey/Hurley regions. Reports from the Coquihalla suggest there's less than 1 m of snow in most avalanche areas. On the surface, fairly widespread surface hoar development has been reported. Below this, a small amount of recent storm snow overlies a thick rain crust. In the north, we have very limited observations. That said, I expect a deeper, more complex snowpack where well settled storm snow overlies a mix of crusts and facets which formed in November.

Problems

Storm Slabs

Forecast new snow and strong winds may develop windslabs in the alpine and at treeline. Loose dry snow may also slide easily off of the old hard crust/surface hoar combination.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid freshly wind loaded features.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Deep Persistent Slabs

Although deeply buried persistent slabs have become more difficult to trigger, avalanches that release on deeply buried crystals would likely be large and destructive in nature. Use extra caution on steep, unsupported alpine terrain.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of thin areas that may propogate to deeper instabilites.>

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

Valid until: Dec 19th, 2014 2:00PM