Avalanche Forecast

Issued: Jan 5th, 2019 4:56PM

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

Avalanche Canada ghelgeson, Avalanche Canada

Human triggered avalanches are the primary concern Sunday. The best and safest riding will be found in the trees on slopes that have soft snow without any slab properties. Stay relatively conservative as the snowpack continues to adjust.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

Moderate onshore flow will continue Sunday across the province maintaining flurry activity and bringing mostly cloudy conditions with a few sunny breaks. SATURDAY NIGHT: Freezing level holding near valley bottom, strong southerly wind, 1 to 5 cm of snow possible.SUNDAY: Overcast, freezing level holding near valley bottom, light southerly breeze at most elevations with moderate southwest wind at ridgetop, 3 to 8 cm of snow possible.MONDAY: Broken cloud cover at dawn thinning to just a few clouds in the late afternoon, freezing level at valley bottom, light west/northwest wind with moderate gusts at ridgetop, trace of snow possible.TUESDAY: Clear skies at dawn with cloud cover steadily increasing through the day, freezing level at valley bottom, light variable wind for most of the day at all elevations, trace of snow possible.

Avalanche Summary

As skies cleared on Saturday we received reports of a widespread natural storm slab avalanche cycle.  The large (size 2 to 3) avalanches likely ran on both Thursday and Friday.Also on Friday, there was a report of a snowmobile triggered avalanche at Allan Creek south of Valemount. The avalanche was size 2 (40 cm deep) on an east aspect at 2100 m.Prior to the storm, several small human triggered avalanches were reported in the region, including small slabs (30 cm thick) on buried surface hoar at Sugar Bowl (see this MIN report for details). This layer is now buried much deeper, and at this point it's uncertain whether it could still be reactive.

Snowpack Summary

An intense storm delivered 50 to 80 cm of snow between Wednesday and Friday. The new snow is rapidly settling at lower elevations, while at higher elevations it continues to get blown around into fresh wind slabs.Prior to the storm, a widespread layer of surface hoar was reactive around treeline elevations. This layer is now 50 to 100 cm deep, and there is some uncertainty about whether it will still be reactive.Another layer buried 150 to 200 cm composed of weak facets, surface hoar, and a sun crust is believed to be gaining strength. Places that might still challenge this assumption would be steep north and east facing slopes between 1900 and 2300 m and steep south-facing slopes in the alpine.The probability of triggering other deep layers in the snowpack is low, but the most suspect areas would be shallow spots in steep rocky terrain.

Problems

Storm Slabs

An icon showing Storm Slabs
Watch for newly formed and reactive wind fueled storm slabs which may remain sensitive to human triggering, especially in the alpine. These will be most sensitive immediately lee of ridgecrest and behind mid-slope terrain features like ribs.
Expect slab conditions to change drastically as you move into wind exposed terrain.Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.Back off if you encounter whumpfing, hollow sounds, or shooting cracks.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 2.5

Valid until: Jan 6th, 2019 2:00PM

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