Archived

Avalanche Forecast

Dec 19th, 2017–Dec 20th, 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

1: Low

The avalanche danger rating at treeline will be low

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

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: South Coast.

Fresh storm slabs may bond poorly to the latest melt-freeze crust in the North Shore mountains - watch for how the new snow is bonding to the old surface. Farther north, be alert for signs of instability in the alpine.

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

After Tuesday's storm it will clear up and we'll have dry weather with cool temperatures for the foreseeable future.WEDNESDAY: Sunny with occasional cloudy periods. Ridge wind moderate northerly. Freezing level 600 m.THURSDAY: Some clouds and isolated flurries. Ridge wind moderate from the north west. Temperature near -3. Freezing level 400 m. FRIDAY: Sunny. Ridge wind moderate from the north east. Temperature near -4. Freezing level 400 m.

Avalanche Summary

Rain on Sunday night and subsequent cooling on Monday 'locked up' the upper snowpack and avalanche activity tailed off.Avalanche activity may increase with 15-20cm snow forecast to fall on Monday's melt-freeze crust. Winds blowing snow around can significantly increase snowfall amounts on down wind (lee) features, so keep a close eye on storm snow amounts as you travel.

Snowpack Summary

Temperatures got quite warm at the tail end of Sunday's storm, with up to 30mm rain falling on 15-20cm snow. Clearing overnight into Monday morning resulted in a widespread melt-freeze surface crust up to the highest treeline elevations. Since then, we've had 20cm snow by Tuesday afternoon. Some key questions to consider are "How well is the new snow bonding to the old surface?" and "Are there areas with deep wind-loaded pockets?"Below tree line the snow pack is thin and there are many early season hazards. Snowpack depths range from 40 cm at 800 m elevation to 200 cm at 1220 m.

Avalanche Problems

Storm Slabs

Tuesday's storm snow will be falling on a widespread melt-freeze crust that exists to upper tree line elevations. Keep a close eye on how the new snow is bonding to the old surface.

Avoid steep convex slopes.Watch for signs of instability such as whumpfing, cracking or recent natural avalanches.Use caution in down wind (lee) areas. Wind loading may create pockets of wind slab.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2