Avalanche Forecast

Issued: Apr 3rd, 2015 8:49AM

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

Purcells.

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, petering to flurries on Sunday and Monday, with a chance of sun. The freezing level is around 1600 m by day, falling towards valley floor by night. Winds are generally light.

Avalanche Summary

Several cornice falls have been reported in the last few days, some of which have triggered slabs on slopes below.On Wednesday, a size 2 persistent slab was triggered in a permanently closed area at a ski area. It may have started in the March persistent weak layer before it stepped down to fail at ground. While the likelihood of triggering a large persistent slab avalanche has gone down, the consequences remain high.

Snowpack Summary

Recent 10-25 cm snow was shifted by variable strong winds into wind slabs on lee slopes above about 2000 m. Cornices are large and touchy in some spots. The new snow sits over various crusts which formed recently. Low elevations sport an isothermal snowpack, which is now be capped by a refrozen crust.Persistent weak layers in the upper snowpack remain a concern. In the north of the region, the mid-March crust/facet layer is down 40-60cm. The mid-February crust/facet/surface hoar layer, down about 80 cm, may also still be reactive in isolated areas. Weak layers which formed earlier in the winter are also a concern in certain spots.

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 areas of wind loaded snow.>Be cautious as you transition into wind affected terrain.>

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.>Avoid steep slopes below cornices.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 5

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