Avalanche Forecast

Issued: Jan 20th, 2012 9:15AM

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

Avalanche Canada jlammers, Avalanche Canada

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather is uncertain on Saturday

Weather Forecast

Saturday: 10-15cm of snow - Moderate to strong southwest winds - Freezing level at 1000mSunday: Some ridging in the morning with trace amounts of snow forecast for the afternoon - Light southwest winds - Freezing level trending from surface to 600m throughout the dayMonday: Light snowfall - Light to moderate west winds - Freezing level at 600m

Avalanche Summary

Ski-cut sluffs to size 1.5 were observed throughout the region on thursday. A few skier-accidental slabs to size 1.5 (30-50 cm crowns) were also observed in the Nelson area. Expect a spike in avalanche activity with Friday night/Saturday's forecast weather.

Snowpack Summary

Average treeline snow depths are nudging over the 2 m mark in this region. In the last seven days, between 40 and 80cm of cold, low density snow has fallen in this region, which has settled to create a storm slab 20-40 cm thick. Cold temperatures have kept the snow light and cohesionless in most areas, although friday night's forecast heavy snow, strong winds and rising freezing levels will add a new load to any buried weaknesses, and create a reactive "upside-down" snow pack.A crust now lies buried around 25-45 cm below the snow surface at elevations below 1900 m. Some areas reported this crust had a layer of surface hoar on it when it was buried. Occasional reports of small soft slab avalanches that have started to come in indicate this slab is starting to be become sufficiently cohesive to produce slab avalanches. There is a blog posting on the Forecaster Blog (link on the sidebar on the left) that discusses this issue in more depth. The mid-December surface hoar/facet persistent weakness, now down 70-120 cm, remains a concern only for very heavy triggers in thin slab areas.

Problems

Wind Slabs

An icon showing Wind Slabs
Forecast wind, snowfall and rising temperatures will create significant reactive wind slab development on cross-loaded and lee terrain.

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

Elevations: Alpine, Treeline.

Likelihood

Likely - Very Likely

Expected Size

1 - 5

Storm Slabs

An icon showing Storm Slabs
Forecast temperatures, wind and snow will add load and reactivity to a storm slab that has been developing throughout the week.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 6

Valid until: Jan 21st, 2012 8:00AM