Archived

Avalanche Forecast

Mar 13th, 2016–Mar 14th, 2016

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

The likelihood of triggering an avalanche will increase with the snow and wind forecast for Monday.

Weather Forecast

MONDAY: snow starting overnight with 10-15cm expected by the end of the day, light to moderate southwesterly winds, 1000m freezing level. TUESDAY: light to moderate snowfall continues, moderate to strong westerly winds, 800m freezing level. WEDNESDAY: flurries, light and variable winds, 800m freezing level.

Avalanche Summary

New snow may cover lingering wind slabs that are still be reactive to human triggering on Monday. Several natural and artificially triggered cornice collapses in the last week have caused large avalanches in the alpine. On Thursday, a natural size 3.5 persistent slab avalanche was reported in Bear Pass. This avalanche occurred on a northwest aspect at 1350m elevation and released on the late-February surface hoar layer.

Snowpack Summary

Ongoing light snowfall and southerly wind have formed hard or soft wind slabs at treeline and in the alpine. Moist snow can be found at lower elevations and on solar aspects. A layer of surface hoar or facets down 70-100cm can be found in areas north of Stewart sitting below Marchs accumulated storm snow. Recent avalanche activity suggest that we may be approaching a critical load on this interface. An older crust/facet layer buried in early February can now be found around 80-120 cm below the surface although this layer has been dormant recently. Cornices are reported to be large and fragile.

Avalanche Problems

Wind Slabs

New wind slabs are expected to form through the day on Monday and may become more reactive with daytime warming and/or sun exposure.

Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

Cornices

Cornices are large and weak. I wouldn't linger on any alpine slopes with overhead hazard nor would I venture too close to ridge edge.

Give cornices a wide berth when travelling on or below ridges.>Extra caution needed around cornices with current conditions.>

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 2 - 5

Persistent Slabs

A layer of buried surface hoar or facets down 70-100cm has recently been reactive around Stewart and north. An old weak crust layer down over 1m is still a concern in the south of the region.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a big slope.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6