Avalanche Forecast

Issued: Jan 26th, 2019 4:59PM

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

Avalanche Canada cgarritty, Avalanche Canada

Don't be too deceived by all the rain. Thick storm slabs have been forming at higher elevations in the region. New snow depths increase with elevation, so increase your caution as you ascend and be mindful of overhead hazards.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Saturday night: Decreasing cloud with easing flurries finishing with a trace of new snow. Winds easing to light northwest.Sunday: A mix of sun and cloud. Light northeast winds. Alpine high temperatures around -3 with freezing levels back to 1000 metres or lower.Monday: Cloudy with sunny periods. Light variable winds. Alpine high temperatures around -3.Tuesday: Mainly cloudy with scattered flurries bringing a trace to 5 cm of new snow. Light to moderate southwest winds. Alpine high temperatures around -1 with a possible above freezing layer at around 1500 metres.

Avalanche Summary

No new avalanches have been reported in the south of the region, where the bulk of Friday's precipitation fell as rain. Further north in the Bear Pass area, more consistent snowfall allowed for observations of several large (size 2-3) wind slabs releasing naturally from steep alpine features. Rain on dry snow at lower elevations was observed triggering natural persistent slab releases over the roughly 50 cm-deep surface layer described in our snowpack summary.A large (size 2.5) wind slab was triggered remotely (from 20 metres away) just south of the Seven Sisters Provincial Park area on Wednesday. This occurred on a southeast aspect at 1700 metres and is believed to have failed on the same surface hoar layer referenced above.Looking forward, continuing snowfall and strong winds will be layering new storm slabs on higher elevation slopes.

Snowpack Summary

In high alpine areas and further north toward Bear Pass, 20-30 cm of new snow (with more new snow on the way) has covered a new layer of surface hoar that may coexist with a crust on sun-exposed slopes. Below the new snow interface, around 50 cm of recent storm snow covers a variable surface of wind-affected, faceted snow and possibly a weak layer of surface hoar in protected alpine areas. Below about 1500 metres (closer to 1000 metres in Bear Pass), the recent storm snow mentioned above is a bit thinner (25-50 cm), more likely rain-saturated, and overlying a more widespread rain crust/surface hoar combination. Reports from the Shames area suggest a good bond between this now saturated surface layer and the supportive underlying crust. Avalanches were observed failing on this layer below treeline in the Bear Pass area on Friday.Below the interface described above, the mid snowpack is strong. For most of the region, a weak layer of facets (sugary snow) buried in early December exists down 180-250 cm. The likelihood of triggering this layer is generally low, but it could be triggered by humans in shallow snowpack areas, particularly in the north of the region.

Problems

Storm Slabs

An icon showing Storm Slabs
The warm, wet, and windy storm formed new storm slabs at higher elevations. These will likely remain reactive to human triggers on Sunday. Storm slabs may step down to a more deeply buried persistent weak layer to create even larger avalanches.
If triggered, storm slabs may step down to deeper layers and result in even larger avalanches.Be especially careful around thick, wind-loaded pockets near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 27th, 2019 2:00PM

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