Archived

Avalanche Forecast

Feb 28th, 2016–Feb 29th, 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

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

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

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.

Moderate winds have loaded lee features in exposed terrain and isolated pockets of storm slab may be lingering on steep slopes.

Confidence

Moderate

Weather Forecast

MONDAY: flurries with accumulations of up to 5cm overnight and 3cm through the day, light to moderate westerly winds, 1000m freezing level. TUESDAY: isolated flurries possible with a clearing trend, moderate westerly winds, 1200m freezing level. WEDNESDAY: mainly sunny, light southerly winds, 1200m freezing level.

Avalanche Summary

Natural avalanche activity had slowed before Sunday's storm. A couple of recent standout avalanches from the North of the region are worth keeping in mind though. On Wednesday two very large wind slab avalanches are suspected to have run on the early February crust in the Bear Pass highway corridor. On Saturday a ski cut on a shallow unsupported roll produced a smaller avalanche, again on the early February crust. No new avalanches had been reported on Sunday when this bulletin was published. However, I suspect that there was a cycle of natural avalanche activity through the day given the moderate snowfall and wind.

Snowpack Summary

New snow and moderate winds have created fresh storm slabs at all elevations and wind slabs at treeline and in the alpine. Up to 50cm of new snow now sits above old wind effected snow, a crust on sunny aspects, or surface hoar in isolated sheltered and shady locations. An old crust buried around February 12th that extends up to about 2000m can now be found down 60-80cm. Below this, a layer of surface hoar buried late in January remains a lingering concern in the far North of the region. The snowpack at lower bellow treeline elevations may now be too shallow for avalanches in many places.

Avalanche Problems

Storm Slabs

Given the recent snowfall and winds I suspect that you can find reactive soft slabs in steep unsupported terrain at most elevations and in wind loaded features in the alpine and at treeline.

Avoid freshly wind loaded features.>Be alert to conditions that change with aspect and elevation. >Choose well supported terrain without convexities.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Persistent Slabs

Buried weak layers remain a concern depending on where you are in the region. In thin snowpack areas, large avalanches can still be triggered from thin spots or by heavy loads such as a cornice collapse or smaller avalanche.

Avoid convexities or areas with a thin or variable snowpack.>Be aware of the potential for large, deep avalanches due to the presence of buried weak layers.>Dig down to find and test weak layers before committing to a big line. >

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 3 - 6