Archived

Avalanche Forecast

Mar 17th, 2013–Mar 18th, 2013

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

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

Unsettled conditions will continue through Monday night with light precipitation and moderate NW wind in the alpine. Periods of more intense snow and gusty winds are also expected. Temps will stay below -5, and in the alpine lower to -15. On Tuesday, a brief ridge of high pressure will bring sunny periods and light SW winds before the next storm.

Snowpack Summary

Dense snow was rapidly deposited on a reactive layer down 55-65cm, which consists of a variety of surfaces including small surface hoar and crust. The storm snow is wet below 1650m and moist to 2000m. At treeline and above, sustained winds have further loaded slopes and formed windslabs. A surface hoar layer down 1.2m continues to be monitored.

Avalanche Summary

Yesterday, 1 size 2.5 natural avalanche was observed on a SE aspect at 2000m. During last weeks storm, numerous avalanches were observed running to valley bottom with many in the size 3.5 range. Cracking has been reported when ski cutting steep, supported rolls. A slab avalanche 65cm deep was triggered by loading snow. The debris was 1.5m.

Confidence

Avalanche Problems

Storm Slabs

Last weeks storm rapidly deposited 50-60cm of heavy, moist snow at treeline. This was deposited on low density snow sitting on a crust and/or surface hoar and is weakly bonded. At lower elevations, rain saturated snow will have refrozen.

Choose well supported terrain without convexities.Breakable crust makes for tough ski conditions.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 2 - 4

Persistent Slabs

It will likely take a large trigger, like a cornice fall or another avalanche to trigger the surface hoar/crust layer from February down 1-1.5m. If triggered, however, the resulting avalanche would be very large and destructive.

Do not travel on slopes that are exposed to cornices overhead.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: 3 - 4

Wind Slabs

Sustained S-SW winds have been forming windslabs on lee terrain above treeline. In these areas, deeper pockets of loaded snow will be more easily triggered.

Use caution in lee areas in the alpine. Recent wind loading have created wind slabs.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine.

Likelihood: Possible

Expected Size: 1 - 3