Avalanche Forecast

Issued: Apr 2nd, 2015 8:33AM

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 still on the radar, but shifting into a low-probability/ high-consequence situation. Be confident in your local snowpack before committing to any big terrain.

Summary

Confidence

Fair - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

Light snow starts on Friday night and continues through the weekend. (Estimates: 5-10 cm on Saturday; 1-5 cm on Sunday). Light flurries continue on Monday. The freezing level is around 1600 m by day, falling towards valley floor by night. Winds are generally light.

Avalanche Summary

Persistent slab, storm slab, and loose wet avalanche activity has tapered off recently. While the likelihood of triggering a large avalanche has gone down, the consequences remain high. 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. Stability is generally expected to improve with the cooling trend but this may take a few days at higher elevations.

Snowpack Summary

10-20 cm 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. Several persistent weak layers exist in the upper metre of the snowpack which remain a concern. The mid-March crust/facet layer is down around 60 cm and has been reactive to light triggers recently. Down around 80 cm is the mid-February crust/facet/surface hoar layer which has also been reactive to heavy loads like avalanches in motion stepping down, cornice failures, or explosives.

Problems

Wind Slabs

Recent winds have shifted snow into wind slabs on lee and cross-loaded slopes. Cornices may be fragile.

Use ridges or ribs to avoid pockets of wind loaded snow.>Be cautious as you transition into wind affected terrain.>Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Persistent Slabs

Buried persistent weak layers may still be reactive to human-triggering and large avalanches remain possible. Smaller avalanches in motion or a cornice failure could step down to one of these deeper layers.

Dig down to find and test weak layers before committing to a big line.>Caution around convexities or areas with a thin or variable snowpack.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

3 - 6

Valid until: Apr 3rd, 2015 2:00PM