Avalanche Forecast

Issued: Apr 3rd, 2015 8:56AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs and Persistent Slabs.

pgoddard, Avalanche Canada

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.

Summary

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 itÂ may still be possible to trigger one of these, causing a very large 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

Valid until: Apr 4th, 2015 2:00PM