Avalanche Forecast

Issued: Jan 24th, 2018 4:01PM

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

Avalanche Canada jsmith, Avalanche Canada

Additional snow and wind Wednesday night will continue to create touchy storm slabs reactive to human triggers. If triggered, these slabs have the potential to step down to deeper weak layers buried in the snowpack, resulting in large avalanches.

Summary

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

WEDNESDAY NIGHT: 10-20cm of new snow / Moderate to strong southerly ridgetop winds / Freezing level around 1000m.THURSDAY: Mostly cloudy with isolated flurries / Light to moderate southerly ridgetop winds / Freezing level dropping to 800m.FRIDAY: Mostly cloudy with flurries; 3-5cm / Light to moderate southwesterly ridgetop winds / Freezing level dropping to valley bottom with an alpine high of -8.SATURDAY: 5-15 cm of new snow / Moderate southerly ridgetop winds / Alpine high of -4.

Avalanche Summary

On Tuesday, a skier triggered size 2 persistent slab avalanche was reported in the Rossland area. No further information was reported but it is suspected to have failed on the surface hoar layer buried in early January which was down 75cm. The slope that slid was low angle and the slab propagated across the entire slope. Additionally, a snowcat northwest of Nelson triggered two size 2.5 persistent slab avalanches on the same early January surface hoar layer which was down around 80 cm at 2250m. Forecast new snow and wind Wednesday night will promote ongoing storm slab avalanche activity, especially in higher elevation, lee terrain.

Snowpack Summary

20-25cm of new snow brings recent storm snow total to approximately 45-60 cm which has been redistributed by strong southerly winds. This overlies the most recent crust and surface hoar (weak feathery crystals) layer that was buried mid-January. This crust can be found on solar aspects while the surface hoar has been buried on shaded aspects above 1600m. Below this layer lies a second crust/surface hoar interface buried early-January that is now 70-100 cm below the surface. The mid-December surface hoar layer is buried 100-130 cm below the surface. This spooky layer still produces "sudden" test results and is most pronounced at treeline, but is also present below treeline . Two laminated crusts created by rain events in late November lay just below the mid-December interface, and may co-exist with facets.

Problems

Storm Slabs

An icon showing Storm Slabs
Additional snow and wind Wednesday night will continue to create touchy storm slabs reactive to human triggers. If triggered, these slabs have the potential to step down to deeper weak layers buried in the snowpack.
Be cautious when transitioning into wind effected terrain.Use small slopes with low or no consequence to test the bond of the new snow.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
The snowpack is complex and has produced very large avalanches on up to four separate weak layers buried 50 to 140cm below the surface. A conservative approach and moderate-angled, simple terrain are good ways to manage a complex snowpack.
Be mindful that deep instabilities are still present and have produced recent large avalanches.Be aware of the potential for large avalanches due to the presence of buried surface hoar.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 3

Valid until: Jan 25th, 2018 2:00PM

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