Avalanche Forecast

Issued: Jan 13th, 2019 5:48PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Slab avalanches may be increasingly sensitive to human triggering in the alpine Monday as warm temperatures reach their apex. Minimize exposure to steep slopes receiving direct sunshine.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

A classic temperature inversion will be with us through Monday evening. No significant precipitation is expected until possibly Friday.SUNDAY NIGHT: Clear skies, temperature inversion with cold (below freezing) air in the valleys and above freezing temperatures between 1800 and 3200 m, alpine temperatures between 0 and +5 are expected, light northwest wind, no significant precipitation expected.MONDAY: Clear skies, temperature inversion with cold (below freezing) air in the valleys and above freezing temperatures between 1500 and 3000 m, alpine temperatures between 0 and +5 are expected, light southwest wind at most elevations with moderate northwest wind at ridgetop, no significant precipitation expected.TUESDAY: Mostly clear skies, freezing level at valley bottom, light variable wind, no significant precipitation expected. WEDNESDAY: Scattered cloud cover, freezing level at valley bottom, moderate to strong west/southwest wind, no significant precipitation expected.

Avalanche Summary

On Saturday a size 2 natural deep persistent slab avalanche was observed on a south facing feature around 2100 m, more details here.  There is also a great MIN report from the neighboring Lizard Range where a group of sledders share about their near miss on a steep southwest facing feature at ridgecrest.On Friday we received a great Mountain Information Network observation of natural activity on solar aspects, more details here. A size 2-2.5 natural avalanche was also reported on a north aspect at 2200 m on Friday. This avalanche was likely triggered by a rock fall, and ran on the deep persistent layer at the base of the snowpack.A few size 1 natural and explosives triggered avalanches were reported in the region on Thursday.

Snowpack Summary

10 to 20 cm of recent storm snow has been redistributed by strong winds and has formed wind slabs at upper elevations. This new snow sits on previous hard wind slabs, a scoured and shallow snowpack on exposed ridges, and soft snow in sheltered areas. Large variability in snow depths still exists in the region, ranging from almost no snow to nearly 200 cm in some areas. For average snowpack areas, expect to find weak and sugary faceted snow 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. Warming temperatures and sunshine Monday have the potential to re-activate this layer.

Problems

Deep Persistent Slabs

An icon showing Deep Persistent Slabs
Deeply buried weak layers remain a concern, especially as temperatures rise and the sun comes out. Large loads like cornices may trigger this layer as well, and cornice failures become more likely during warm, sunny conditions.
Use conservative route selection, choose moderate angled and supported terrain with low consequence.Pay attention to overhead hazards like cornices which could trigger the deep persistent slab.Watch for clues, like sluffing off of cliffs, that the snowpack is warming up.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3.5

Storm Slabs

An icon showing Storm Slabs
Slabs may become more reactive as temperatures rise and the sun comes out.
Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Minimize exposure to steep slopes on warm or sunny days.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 14th, 2019 2:00PM

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