Avalanche Forecast

Issued: Dec 7th, 2018 3:37PM

The alpine rating is low, the treeline rating is low, and the below treeline rating is low. Known problems include Persistent Slabs.

Avalanche Canada ghelgeson, Avalanche Canada

Conditions have been steadily improving, but it may be possible to trigger a persistent slab avalanche, especially on steep protected solar aspects where surface hoar coexists with a sun crust.

Summary

Confidence

Moderate - Wind speed and direction is uncertain on Sunday

Weather Forecast

The weather pattern has begun to change on the Coast but it looks like more of the same for the Kootenay Boundary for the foreseeable future.FRIDAY NIGHT: Freezing level at valley bottom, light northwest wind, no significant precipitation expected.SATURDAY: Broken cloud cover, freezing level at valley bottom, light northwest wind, no significant precipitation expected.SUNDAY: Broken cloud cover, freezing level at valley bottom, moderate southwest wind in the alpine, no significant precipitation expected.MONDAY: Overcast, freezing level near valley bottom, moderate southwest wind in the alpine, trace of precipitation possible.

Avalanche Summary

Skiers were able to intentionally kick off small (size 1) loose dry avalanches from a variety of activity aspects around 2100 m Thursday. Several small natural wind slab releases were observed in the Whitewater area on Wednesday. These occurred on steep alpine features and may have been a product of recent northerly winds. Big thanks go out to our contributors to the Mountain Information Network. Please continue to post your observations here.

Snowpack Summary

Days of cold temperatures and increasingly clear skies have been growing a new layer of feathery surface hoar on the surface. Winds may have scoured some of this surface hoar from alpine slopes. The cold has also been transforming our roughly 20 cm of aging storm snow on the surface into a layer of faceted (weak, sugary) snow. At treeline, the height of snow is between about 100 and 140 cm. 40 to 80 cm below the surface there is a closely stacked pair of buried persistent weak layers. The upper layer consists of surface hoar (feathery crystals) in most places, but may present as a sun crust on steep south facing slopes. The deeper layer features similar surface hoar distribution over a more widespread temperature crust. These layers have shown ongoing but variable reactivity in snowpack tests in the past week. Both surface hoar layers are thought to be widespread at treeline and may also extend into sheltered alpine features.At the base of the snowpack is a thick melt-freeze crust that formed near the end of October. Observations of reactivity at this crust have been limited, but it has acted as the failure plane in several large avalanches in the neighbouring South Columbias.

Problems

Persistent Slabs

An icon showing Persistent Slabs
Our 40-80 cm deep weak layer is slowly becoming less reactive, but it's still a concern in steeper, protected slopes around treeline and lower alpine. Special attention should be given to solar aspects where surface hoar may coexist with a sun crust.
Avoid steeper open slopes and convex rolls at treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

1 - 2

Valid until: Dec 8th, 2018 2:00PM

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