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Avalanche Forecast

Apr 3rd, 2015–Apr 4th, 2015
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
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
1: Low
The avalanche danger rating below treeline will be low
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: South Columbia.

The persistent slab problem is shifting into a low-probability/ high-consequence situation. Be confident in your local snowpack before committing to any big terrain.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Sunday

Weather Forecast

Light snow fall (5-15 cm) is expected on Saturday and Sunday, petering to flurries on Monday, with a chance of sun. The freezing level is around 1500 m by day, falling towards valley floor by night. Winds are generally light.

Avalanche Summary

A skier was partially buried in a size 2.5 wind slab on a north aspect at 2600 m on Thursday. Some naturally-triggered wind slabs and cornice falls were also reported. On Wednesday, a naturally-triggered size 2.5 wind slab was observed on a NE aspect at 2500 m. An ice fall also triggered a size 3 deep persistent slab which failed at ground. Human-triggered wind slabs and persistent slabs are still a concern, especially on steep, unsupported slopes in the alpine.

Snowpack Summary

10-20 cm recent dry convective snow was shifted by NW winds into wind slabs on lee slopes in the alpine. These overlie a recently formed crust which varies in thickness with elevation. Below about 2000 m, loose moist snow makes up much of the snowpack underneath a surface crust. Persistent weak layers in the upper snowpack remain a concern. The mid-March crust/facet layer is down around 60 cm. Down around 80 cm is the mid-February crust/facet/surface hoar layer. Both of these layers are slowly improving in strength, although it  may still be possible to trigger one of these, causing a very large avalanche.

Avalanche Problems

Wind Slabs

Wind slabs may be found behind terrain breaks like ridges and ribs. Large cornices may be fragile - give these a respectful berth.
Give cornices a wide berth when travelling on or below ridges.>Use ridges or ribs to avoid pockets of wind loaded snow.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 4

Persistent Slabs

Buried persistent weak layers may still be reactive to human-triggering. Most likely triggers include a person or machine on a thin snowpack spot, or a cornice fall.
Caution around convexities or areas with a thin or variable snowpack.>Dig down to find and test weak layers before committing to a big line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 6