Archived

Avalanche Forecast

Dec 19th, 2013–Dec 20th, 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

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

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Glacier.

Weather Forecast

Today expect a mix of sun and cloud, with cool temps of -15 to -20, and light winds at ridgetop. A low pressure system will move into the region overnight. Tomorrow will be cloudy, with light snow (up to 5cm), and a high temp of -10. Over the weekend expect flurries, light to moderate W winds, and temps ranging from -10 to -4.

Snowpack Summary

Up to 80cm of settled snow sits over a variety of surfaces like surface hoar at lower elevations, facets and variable wind slabs at higher elevations. This interface is reactive in snowpack tests. Strong winds have formed wind slabs and wind loaded pockets at treeline and above. Below this are 2 persistent weak layers and the snowpack is facetted.

Avalanche Summary

Avalanche activity has tapered off now that the storm is over. A widespread natural avalanche cycle occurred over the past 3 days, with avalanches up to size 3.5 being triggered by rapid loading by snowfall and wind transport. Most were initiated in the alpine and at treeline, running well into runouts, but several triggered slabs below treeline.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Wind Slabs

Strong winds throughout the storm, with lots of snow available for transport, have loaded lee slopes and formed wind slabs at treeline and above. Wind slabs may be triggerable; watch for signs like cracking or hollow sounding snow.

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

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 3

Persistent Slabs

The recent snow has tightened up into a slab. It sits on various weak crystals, like facets or surface hoar, that may be triggered by skiers. If triggered, avalanches may step down to deeper surface hoar layers resulting in very large avalanches.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Choose well supported terrain without convexities.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 2 - 4