Avalanche Forecast

Issued: Dec 1st, 2018 4:14PM

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

swerner, Avalanche Canada

Purcells.

Wind slabs may be more reactive to human triggers where they sit above a buried weak layer. Check out the New forecaster blog HERE.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

As the upper ridge sets up, we move into a period of cooling, drying and fairly light northerly winds. SUNDAY: Mix of sun and cloud/ alpine temperatures near -10/ generally light winds from the northeast/ freezing level valley bottomMONDAY: Cloudy/ alpine temperatures near -12/ ridgetop winds light from the northeast/ freezing levels valley bottomTUESDAY: Mix of sun and cloud/ alpine temperatures -15/ ridgetop winds light from the northeast/ freezing levels valley bottom.

Avalanche Summary

Natural loose dry avalanches were reported from steep, rocky terrain features up to size 1. With little for avalanche observations and low confidence of the buried surface hoar distribution, I suspect that human triggered avalanches remain possible, especially where deeper deposits of storm snow or wind slab sit above the buried weak layer. I also suggest keeping the basal crust on your radar. Steeper, thin-thick rocky alpine features are more suspect.If you got out this weekend please submit your observations to the Mountain Information Network.

Snowpack Summary

The early season snowpack is highly variable in this region. Approximately 20 cm of recent snow fell earlier this week which may have been blown into wind slabs on exposed northerly and northeasterly slopes. Expect loose dry, unconsolidated snow sluffing from steeper, rocky terrain features. In some places, there are two layers of feathery surface hoar being reported, one around 20 cm below the surface and one down 35 cm. One or both of these may be associated with a crust on south aspects. The most likely places to trigger one of these layers is in deeper snow areas in shady spots on smooth slopes. A prominent feature of the snowpack is a combination of a crust and underlying sugary, faceted snow found near the base of the snowpack. It may be possible to release an avalanche on smooth slopes in the alpine.

Problems

Wind Slabs

Most likely found on leeward slopes and terrain features. They could be more reactive where they sit above a weak, feathery surface hoar layer.

Caution in lee and cross-loaded terrain near ridge crests.Watch for whumpfing, hollow sounds, shooting cracks or recent avalanches.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Deep Persistent Slabs

A nasty combination of crust and sugary, faceted snow exists at the base of the snowpack in the alpine. This layer could produce avalanches on steep, smooth slopes in the alpine.

Large alpine slopes with a thin-thick, rocky snowpack are suspect to triggering.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Unlikely - Possible

Expected Size

1 - 3

Valid until: Dec 2nd, 2018 2:00PM