Avalanche Forecast

Issued: Jan 6th, 2019 4:26PM

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

Avalanche Canada mbender, Avalanche Canada

Weak layers buried near the bottom of the snowpack remain a concern. A conservative approach to route selection is recommended.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY NIGHT: Mostly cloudy, moderate west winds, alpine temperature -11 CMONDAY: Mix of sun and cloud, light to moderate west winds, alpine temperature -12 CTUESDAY: Cloudy with sunny breaks, light southwest winds, alpine temperature -7 CWEDNESDAY: Cloudy with sunny breaks, light southwest winds, alpine temperature -6 C

Avalanche Summary

A natural avalanche cycle may have occurred in the region with the substantial amount of recent snowfall on Thursday and Friday. Additionally there is a report of an explosives controlled deep persistent slab size 2.5 release on an east aspect at 2100m on Friday and also on Saturday of a size 2.5 explosives controlled wind slab release on a southeast aspect at 2000m.Last Wednesday, a naturally-triggered large (size 3) avalanche was observed near Elkford, which likely released on Tuesday. See here. It ran full-path to valley bottom. In the far west of the region, the snowpack has been observed to be weak and touchy, as described here.

Snowpack Summary

Large variability in snow depths still exists in the region, ranging from practically no snow to almost 200 cm. Upwards of 50-60 cm of snow fell late last week above 1500 m. The snow fell with strong southwest winds. Expect the deepest deposits in the lee of terrain features. This snow will sit on previous hard wind slabs, a scoured and shallow snowpack on exposed ridges, and soft snow in sheltered areas. Below 1500 m, expect to find wet snow that will freeze into a hard crust once temperatures cool.All of this recent snow has loaded a weak snowpack. For average snowpack areas, expect to find weak and sugary faceted grains around 50 to 100 cm deep, which extend to the ground. This weak bottom half of the snowpack has been the culprit for large avalanches in the region over the past few weeks. It will take time for the snowpack to adjust to the added load.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Deeply buried weak layers remain a concern even as the storm snow from last week has settled and bonded. Avalanches triggered on this layer will likely scour to the ground, resulting in large avalanches.
Watch for whumpfing, hollow sounds, shooting cracks, and recent avalanches.Avoid steep convexities or areas with a thin or variable snowpack.Choose low-angled, mellow terrain without any consequences.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Storm Slabs

An icon showing Storm Slabs
Steady south and southwest winds have created reactive wind slabs in the lee of terrain features.
If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: North, North East, East, North West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 7th, 2019 2:00PM

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