Avalanche Forecast

Issued: Jan 21st, 2018 4:35PM

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

Avalanche Canada cgarritty, Avalanche Canada

Intense winds continue to drive the avalanche danger. Persistent slab problems deeper in the snowpack still can't be written off.

Summary

Confidence

Moderate -

Weather Forecast

Sunday night: Scattered flurries bringing 2-5 cm of new snow. Strong southwest winds. Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Moderate southwest winds. Alpine high temperatures around -8.Tuesday: Mainly cloudy. Moderate to strong southwest winds. Alpine high temperatures of -7.Wednesday: Mainly cloudy with scattered flurries and a trace to 3 cm of new snow, continuing overnight. Strong southwest winds. Freezing level rising to 1600 metres with alpine high temperatures of -3.

Avalanche Summary

Reports from Saturday showed explosives control in the Castle area producing several Size 2-2.5 storm slabs around 40 cm deep. Ski cutting in the same area produced numerous smaller (Size 1) releases also confined to the recent storm snow.Looking forward, expect ongoing strong winds to promote lee loading as well as slab formation and reactivity even as snowfall tapers off.

Snowpack Summary

Up to 40 cm of new snow from recent stormy weather has buried both a new layer of feathery surface hoar in sheltered areas as well as sun crust on solar aspects. The new snow will need time to form a reliable bond to this previous surface. Moderate to strong winds have also been encouraging slab formation at higher elevations and continuously loading loose snow into deeper wind slabs in lee areas. Beneath the new snow, Previous southwest winds formed wind slabs that are now buried in lee terrain at higher elevations.Down about 60-80 cm, weak layer of feathery surface hoar crystals and/or sun crust from mid-December is found at treeline and below treeline elevations. Deeper in the snowpack, another weak early-season layer of rain crust and sugary facets exists. Slabs may still fail on these layers under the weight of a person, a machine, or large wind slab release. Although the snowpack structure is variable across the region, these persistent slab problems are generally widespread. Snowpack depths are across the region are similarly variable, but typically shallower in the east.

Problems

Wind Slabs

An icon showing Wind Slabs
Cranking southwest winds have been transporting recent snow into increasingly thick and reactive wind slabs in lee areas. Slabs that form in openings at lower elevations may overlie a layer of touchy surface hoar.
Whumpfing, shooting cracks and recent avalanches are all strong indicators of unstable snowpack.Southwest winds will likely form thicker, more sensitive slabs on northeast aspects.If triggered, wind slabs may step down to deeper layers and result in large avalanches.

Aspects: North, North East, East, South East, South.

Elevations: All elevations.

Likelihood

Likely - Very Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
Persistent slab activity has been declining, but potential still exists for large avalanches to be triggered on deeply buried weak layers. Stress on deep weak layers will increase as intense southwest winds continue to load lee areas.
Back off if you encounter whumpfing, hollow sounds, or shooting cracks.Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

1.5 - 3

Valid until: Jan 22nd, 2018 2:00PM

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