Avalanche Forecast

Issued: Feb 4th, 2018 6:22PM

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.

Avalanche Canada ghelgeson, Avalanche Canada

Storm slabs are expected to remain sensitive to human triggering and a window of sun Monday afternoon could initiate a round of natural avalanche activity. Take a cautious approach and minimize your exposure to overhead avalanche terrain.

Summary

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

A strengthening ridge axis on Monday offers a brief lull in the action before the next system slams into the Northwest Coast on Tuesday, bringing significant snow and wind that is expected to last through Wednesday night. MONDAY: Overcast with some clearing in the afternoon, freezing level at valley bottom, light to moderate northwest wind, trace of snow possible. TUESDAY: Overcast, freezing level at valley bottom, moderate to strong west/southwest wind, 15 to 25 cm of snow. WEDNESDAY: Overcast, freezing level around 750 m, moderate to strong southwest wind, 15 to 30 cm of snow.

Avalanche Summary

On Saturday wind and storm slab avalanches failed naturally to size 2 on a variety of aspects in both alpine and treeline elevation bands.  A natural size 3 persistent slab avalanche was observed on a steep north facing alpine feature with a crown up to 100 cm in depth, which suggests the mid-January interface was involved.  A another very large avalanche (size 3.5) was reported from an unknown aspect/elevation.  Natural avalanche activity was observed on Friday morning, producing several 30 cm thick slabs in the latest snow. A large (size 3) storm slab avalanche was reported on a east aspect east of Terrace.A few persistent slab avalanches released on Wednesday, most likely failing on the mid-January crust. This included a natural size 3 avalanche on a southwest slope at 1150 m near Exstew and a few skier triggered slabs (size 1-2) in thinner snowpack areas (east of Terrace and the northern part of the region). Overall, activity on persistent weak layers has been limited, but large persistent slab avalanches may remain possible during periods of heavy loading or rapid warming.

Snowpack Summary

The weekend storm produced up to 35 cm of new snow, the region has now received up to a metre of snow over the past week, but warm temperatures have promoted settlement and reduced this amount to 50-70 cm. Westerly winds are forming fresh wind slabs in exposed terrain.A weak layer buried in mid-January is 60-100 cm below the surface and remains a concern. In most areas this layer is a crust, but it may also be surface hoar in sheltered areas at treeline and below. This layer produced a few human triggered avalanches throughout the region over the past week, and may remain reactive as it adjusts to the weight of the new snow.In thinner snowpack areas (north and inland), deeper crust / surface hoar layers that were buried in December and early January may still be a concern. They are buried over 100 cm below the surface, but may be triggerable from thin spots.

Problems

Storm Slabs

An icon showing Storm Slabs
Significant snow and wind have formed storm slabs that are expected to be most reactive at higher elevations and in wind-affected terrain.  A window of sun Monday afternoon could initiate a fresh round of natural avalanche activity too.
Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Minimize exposure to sun exposed slopes receiving direct solar radiation.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak layer exists 60-100 cm below the surface. It may still be possible for humans to trigger persistent slab avalanches on this layer, and storm slab avalanches could step down to this layer.
Avoid lingering in runout zones.Avoid areas with overhead hazard.Caution around convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Feb 5th, 2018 2:00PM

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