Avalanche Forecast

Issued: Feb 7th, 2017 4:47PM

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

Avalanche Canada cgarritty, Avalanche Canada

Keep watching for signs of instability and changing conditions as you gain elevation. The conditions still require conservative terrain selection. Wind exposed areas are the most concerning.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

Wednesday: A mix of sun and cloud with flurries beginning late afternoon. Winds light from the south. Alpine temperatures of -9.Thursday: Periods of snow delivering 15-25 cm of new snow. Winds moderate to strong from the south. Freezing level rising to 1500 metres with alpine temperatures of -2Friday: Flurries bringing approximately 5 cm of new snow. Winds strong from the southwest. Freezing level to 1200 metres with alpine temperatures of -6.

Avalanche Summary

Reports from Monday are a continuation of what we've seen over Saturday and Sunday, with ample observations of Size 1-2 storm slabs being triggered on all aspects both naturally and with ski cutting. Several Size 2.5 slides ran naturally east of Nakusp and a few remotely triggered Size 1 slides were also observed in different ranges within the region. The general character of these avalanches has been described as soft or very soft slab, with a number of recent observations indicating they have been very reactive to skier traffic, fast-running, and capable of entraining large amounts of loose snow.As for Wednesday's outlook, our storm slabs should be expected to remain sensitive to skier and rider triggers, especially where they overlie weak layers present at our previous surface and where exposure to wind has promoted slab formation. Loose snow avalanches have also been an ongoing hazard for the past few days and should not be underestimated in steeper and confined terrain, especially where the potential exists to entrain significant mass.

Snowpack Summary

Up to 10 cm of new, low density snow on Monday night (coupled with 30 cm from Sunday night) has brought our new snow totals from the past few days to a wide-ranging 40-90 cm. The deepest accumulations appear to be focused near Goat Range Provincial Park. Our new snow has buried a range of different surface conditions that developed last week. These previous surfaces include wind slabs on a variety of aspects in wind-exposed terrain, sun crust on steep solar aspects, faceted snow, as well as surface hoar found growing on sheltered open slopes in the days before the storm. The bond of the new snow to these underlying surfaces will take some time to form, and touchy conditions should be expected both at this interface as well as at mid-storm interfaces within the new snow over the short term. A persistent weakness buried mid January is now down 50-120 cm and consists of buried surface hoar in sheltered areas, sun crust on south aspects, and/or widespread faceted old snow. It has generally stabilized but may be sensitive to triggering in isolated areas where buried surface hoar is preserved. The mid and lower snowpack are generally well settled and stable.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs have recently formed over a wide range of weak surfaces. These slabs can be expected to remain reactive to human triggers, especially on unsupported slopes and where wind effect has promoted slab formation.
Watch for signs of instability such as whumpfing, or cracking. Choose well supported terrain without convexities.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Feb 8th, 2017 2:00PM