Archived

Avalanche Forecast

Mar 12th, 2013–Mar 13th, 2013

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

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

4: High

The avalanche danger rating in the alpine will be high

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Northwest Coastal.

Confidence

Good

Weather Forecast

Wednesday: 10-15cm of snow is expected with freezing levels remaining in valley bottoms and moderate southeasterly winds. Thursday: Another 10cm or so of new snow, with freezing levels remaining in valley bottoms and light to moderate southerly winds. Friday: 20-30cm of new snow with freezing levels remaining in valley bottoms and moderate southerly winds.

Avalanche Summary

Reports from Monday include several small human-triggered loose snow and soft wind slab avalanches involving the recent storm snow.

Snowpack Summary

15-25cm of unconsolidated new snow is bonding poorly a variety of old surfaces which include: a crust at lower elevations and on solar aspects; old wind slabs in exposed areas, and fairly widespread large surface hoar. Moderate to locally extreme west/southwest winds have redistributed the new snow into soft and hard wind slabs in exposed terrain. This new snow is currently reactive to human triggers primarily where cohesive wind slabs have formed, but reactivity is expected to become more widespread as the overlying slab develops with continued loading. The mid snowpack layers are generally well settled and strong. Facets at the base of the snowpack may resurface as a concern now that spring warming is on the doorstep and full-depth releases are becoming more likely (primarily in the northern part of the region).

Avalanche Problems

Wind Slabs

Light snow and strong winds have created new wind slabs in exposed terrain. Wind slabs may be particularly reactive in areas where they overlie a weak layer of buried surface hoar.

Be cautious as you transition into wind affected terrain.>Avoid freshly wind loaded features.>Choose conservative lines and watch for clues of instability.>Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4