Archived

Avalanche Forecast

Mar 3rd, 2013–Mar 4th, 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.

As the storm passes, and loading by wind and snow slows, natural avalanche activity will decrease. It will take time, however, for the snowpack to adjust to the new load. You might be all it takes to overload it, with severe consequences.

Weather Forecast

Light flurries, cooling temps and moderate to strong S'ly (N'ly at mountain top) winds are expected today as the storm leaves the region. A brief ridge of high pressure will bring a mix of sun and cloud and light winds for Monday. S'ly winds will increase again as another low pressure system arrives overnight on Monday. With light snow on Tues.

Snowpack Summary

60cm of heavy, moist snow fell in 48hrs and rapidly loaded the Feb 12 surface hoar/crust layer down ~1m. The surface snow is wet to 1400m and moist to at least 1900m. In the alpine, S'ly winds are transporting snow, rapidly loading slopes and forming new windslabs. Cooling temps will help to start strengthening the snowpack, but it will take time.

Avalanche Summary

Natural avalanche activity continued yesterday.Â 15 size 2-3 avalanches were observed along the highway, with moist debris and running well into the avalanche fans. The large avalanche cycle during the storm (see yesterdays bulletin) occurred on the storm interface and Feb 12 layer. None appear to have stepped down to deeper layers.

Confidence

Avalanche Problems

Storm Slabs

60cm of heavy storm snow is settling into a cohesive slab. Loading by wind and snowfall continues to trigger large avalanches. The snowpack needs time to adjust to the new load and will still be touchy to human triggering.

The new snow will require several days to settle and stabilize.Good day to make conservative terrain choices.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 2 - 3

Persistent Slabs

A weak surface hoar layer is now down ~1m. This layer has caused widespread avalanches: natural's up to size 4, and size 2.5 human triggered avalanches. In areas where it hasn't already avalanched it is very reactive, and has been remotely triggered.

Avoid paths that have not avalanched recently.Avoid open slopes and convex rolls at and below treeline where buried surface hoar may be preserved.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 2 - 4

Wind Slabs

Moderate to strong southerly winds continue to transport snow. This is loading lee slopes, overloading the snowpack and triggering large avalanches, as well as forming windslabs on exposed slopes. These areas will take even more time to stabilize.

Avoid freshly wind loaded features.Minimize overhead exposure; avalanches triggered by windloading may reach run out zones.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 3