Archived

Avalanche Forecast

Jan 22nd, 2015–Jan 23rd, 2015

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

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

4: High

The avalanche danger rating at treeline will be high

Below Treeline

3: Considerable

The avalanche danger rating below treeline will be considerable

Regions: Glacier.

A touchy layer, with remote triggering potential means that you need to be aware of who is above and below you, minimize your exposure, and regroup in safe spots. Cautious terrain selection and good group management are essential.

Weather Forecast

Flurries are starting as a series of weather systems move into the region. Today expect trace of snow, with moderate SW winds and freezing levels rising to 1300m. Steady snow starts on Friday; we expect 25cm by the end of the day with freezing levels to 1600m and strong winds. Sat expect another 14cm, freezing levels at 1700m and moderate SW winds.

Snowpack Summary

A 60cm slab sits on the Jan 15 surface hoar. It will be deeper in lee features where loaded by south winds. The Jan 15 was widespread, largest at treeline, and on solar aspects sits on a sun crust. Tests indicate it is likely to be triggered (CTE SC) and propagate (PST 29/100 end). The Dec 17 surface hoar is down 100-150cm and stubbornly reactive.

Avalanche Summary

On Tuesday artillery control triggered over 30 size 2 to 3.5 avalanches from all aspects between 17-2700m. Notables were size 3.5's from the W face of Cheops and off Mt Tupper that ran into the creeks. Human triggered avalanches up to size 2.5 continue to occur in the region. Remote triggering from up to 300m has been reported.

Confidence

Timing of incoming weather systems is uncertain

Avalanche Problems

Persistent Slabs

A 60cm+ thick cohesive slab now overlies a touchy surface hoar layer. Tests indicate that it may be triggered by light loads (ie you) and likely to propagate widely as the slab stiffens. Avalanches have been remotely triggered from up to 300m away.

Watch for whumpfing, hollow sounds, and shooting cracks.Use conservative route selection, choose moderate angled and supported terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 3

Wind Slabs

Strong southerly winds during the storm, with lots of low density snow available for transport, will have formed windslabs in lee areas. These deep pockets of windslab may overlie the touchy surface hoar layer.

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: Possible

Expected Size: 1 - 2

Persistent Slabs

A surface hoar layer, down 1-1.5m, that was buried in mid December continues to be reactive. Avalanche control had a few avalanches stepping down to this layer, even in areas where it had been previously controlled. The new load may wake it up again.

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: Alpine, Treeline.

Likelihood: Possible

Expected Size: 3 - 4