Avalanche Forecast

Issued: Dec 17th, 2018 4:55PM

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

mbender, Avalanche Canada

South Coast Inland.

Forecast precipitation amounts are uncertain Monday night and Tuesday. If new snow amounts are higher locally than indicated, then avalanche danger will be HIGH. Nonetheless a conservative approach to terrain selection is recommended.

Summary

Confidence

Low - Forecast snowfall amounts are uncertain

Weather Forecast

MONDAY NIGHT: Snow, accumulation 10-25cm. Alpine temperature -1. Moderate to strong southwest wind. Freezing level 1200m. TUESDAY: Snow, accumulation 5-10cm. Alpine temperature -2. Moderate to strong southwest wind. Freezing level 1400m. WEDNESDAY: Flurries, accumulation 5cm. Alpine temperature -2. Light west wind. Freezing level 1300m. THURSDAY: Rain in the south and snow in the north, accumulation 20-30cm. Alpine temperature 0. Strong southwest wind. Freezing level 2000m.

Avalanche Summary

Explosive control work along the Duffey Lake road last Friday produced avalanches up to size 2.5 running on the weak layer of facets buried 60 to 80 cm below the surface. A remotely triggered size 1.5 avalanche in the Coquihalla Summit backcountry suggests this same layer is a concern there. No new avalanche activity has been reported since then.

Snowpack Summary

Up to 1 m of new snow fell since the storm pattern started last Sunday. Strong southerly winds distributed new snow into variable wind slabs in exposed locations. A crust at or near the surface likely exists up to approximately 1700 m.Below the recent storm snow lies a weak layer, comprising 20-30 cm of low density faceted snow. Initially, the snow did not bond well to this layer. While it's likely gaining strength, field observations show that slab avalanches remain possible on this layer.Near the base of the snowpack, a crust exists that previously had sugary facets. This could potentially still be of concern in high north facing areas in drier parts of the region. Elsewhere, this layer is no longer a concern.

Problems

Storm Slabs

New snow combined with wind has developed fresh storm and wind slabs.

Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.The new snow will require several days to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

A weak layer buried approximately 70 cm below the surface has the potential to produce large avalanches.

Use conservative route selection, choose moderate angled and supported terrain with low consequence.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Dec 18th, 2018 2:00PM