Archived

Avalanche Forecast

Dec 27th, 2013–Dec 28th, 2013

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

3: Considerable

The avalanche danger rating below treeline will be considerable

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

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

Regions: Glacier.

Rapid loading by snow and wind are forecast later today. Minimize your exposure to avalanche terrain during the storm, including while traveling across paths in the valley bottom. Avalanches have been running fast and far onto avalanche fans.

Weather Forecast

A cold front will pass through the region today. Moderate precipitation rates, with ~8cm accumulation today, mild temps and moderate to strong westerly winds are forecast. These are ideal slab formation conditions. Over the weekend expect mostly cloudy skies, light flurries, and light winds shifting to the NW at ridgetop.

Snowpack Summary

~45cm storm slab sits on a weak layer of large snowflakes which are reactive in tests. The Dec 8 PWL, which is surface hoar at lower elevations and facets and variable wind slabs at higher elevations, is down ~80cm. This layer is becoming less reactive in tests. The Nov 28 surface hoar, down ~1m, is still reactive where it exists.

Avalanche Summary

Recent avalanche activity has been triggered by rapid loading by snowfall and wind-loading, with avalanches to size 2.5 running into avalanche fans.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Wind Slabs

Conditions are ideal for slab formation; strong SW winds, with mild temperatures are forecast. The strong winds will intensify the rate of loading onto lee slopes, and form new windslabs on lee slopes.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Minimize overhead exposure during periods of heavy loading from new snow, wind.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Storm Slabs

Alpine temps rose overnight to 0'C at 1900m, before dropping below freezing again. Recent storm snow will have become more cohesive. There are a few weak layers within this slab. Tests indicate that they may be triggered by light loads, like you.

Good group management is essential to manage current conditions safely.Whumpfing, shooting cracks and recent avalanches are all strong inicators of unstable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 2

Persistent Slabs

Persistent weak layers down ~80cm (facets), and down ~115cm (surface hoar) continue to be reactive in specific locations. Although these interfaces are becoming less likely to trigger it is possible, or smaller avalanches may step down to this layer.

Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.Dig down to find and test weak layers before committing to a line.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4