Archived

Avalanche Forecast

Apr 12th, 2017–Apr 13th, 2017

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

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: South Coast.

New snow and shifting wind directions may create wind slabs on a variety of aspects, including slopes that are generally windward.

Confidence

Moderate - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

THURSDAY: 5-10 mm of rain or 5-10 cm of snow above roughly 1100m. Light Southwesterly ridgetop winds. Freezing level around 1200m.FRIDAY: Mostly cloudy with isolated flurries. Light Southwesterly ridgetop winds. Freezing level around 1200 m.SATURDAY: Sunny. Light southwesterly ridgetop winds. Freezing level around 1500m.

Avalanche Summary

On Thursday the main concern will be wind slabs below alpine ridgetops. At tree line expect small loose wet avalanches in steep terrain if the sun appears for any length of time. Saturday's fatal avalanche on Mt Harvey (near Lion's Bay) was the result of people being on a cornice that failed. A large avalanche was subsequently triggered by the multi-ton snow boulders hitting the slope below.

Snowpack Summary

15-25 mm of precipitation is forecast to fall as snow above roughly 1200 m and as rain below on Wednesday. This means snow in the alpine, rain/snow at treeline, and rain below treeline. Strong southeast winds are expected to accompany the storm and create fresh wind slabs on lee features in the alpine which may be reactive to human triggers. The mix of rain and snow at treeline elevations may create the possibility of loose wet avalanches. Below treeline, rain has saturated an already wet, isothermic snowpack. Cornices are large in some areas and could trigger large avalanches when they fail. Additionally, cornices present a falling hazard and should be given a wide berth while traveling on ridgetops.

Avalanche Problems

Wind Slabs

Expect to find fresh wind slabs reactive to human triggers below alpine ridgetops.

Pay attention to changing conditions with elevation.Use caution in lee areas. Recent wind loading has created wind slabs.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Cornices

Recent snow and wind are growing already large cornices. Minimize your exposure to cornices when it is cold and completely avoid them when it is warm and/or sunny.

Give cornices a wide berth when travelling on or below ridges.Falling cornices can trigger large avalanches.

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

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 1 - 3

Loose Wet

Rain at lower elevations has led to a gradual break down of surface crusts and has contributed to wet snow sluffing and gathering mass in steep terrain.

Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2