Archived

Avalanche Forecast

Dec 26th, 2013–Dec 27th, 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

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

Regions: Glacier.

Avalanches are expected today with snowfall and wind loading weak layers. Avalanches have been running fast and far onto avalanche fans. Minimize your exposure to avalanche terrain, including while traveling across paths in the valley bottom.

Weather Forecast

We should get 10cm of snow today (on top of the 8cm that fell overnight), with strong SW winds gusting to extreme. Freezing levels may rise to 1500m. On Friday, another 10cm of snow is forecast with strong SW winds. Over the weekend, snowfall and the winds should taper off and we may see some sunny breaks.

Snowpack Summary

30cm of settled snow 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 in some locations.

Avalanche Summary

No new avalanches were observed yesterday. Recent avalanche activity has been triggered by wind-loading, with avalanches to size 2.5 running into avalanche fans. As the storm builds, winds are forecast to increase as well. With lots of snow available for transport, wind loading will magnify precipitation rates and natural avalanches are expected.

Confidence

Intensity of incoming weather systems is uncertain

Avalanche Problems

Wind Slabs

Strong SW winds are expected today. They will intensify the rate of loading onto lee slopes and form new windslabs. The new snow will also bury pockets of windslab that have been reactive to skiers in lee and crossloaded terrain.

Avoid freshly wind loaded features.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Storm Slabs

40cm of recent storm snow is settling. Within this slab are layers of large, weak snowflakes that may be triggered by skiers/riders or by rapid loading during the storm. If triggered, this slab may step down to deeper instabilities.

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

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.

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4