Avalanche Forecast

Issued: Apr 2nd, 2015 8:41AM

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 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 - Forecast snowfall amounts are uncertain

Weather Forecast

Light snow starts on Friday night and continues through the weekend. (Estimates: 5 cm on Saturday; 1-5 cm on Sunday; 5 cm on Monday). The freezing level is around 1500 m by day, falling towards valley floor by night. Winds are generally light.

Avalanche Summary

Ongoing 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, some natural cornice falls were observed on shady aspects, some of which triggered slabs up to size 2.5 on the slopes below. Isolated wind slabs were also reported.

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 may now be capped by a refrozen crust.Several persistent weak layers exist in the upper 1m of the snowpack and remain a concern. In the north of the region, the mid-March crust/facet layer is down 40-60cm and remains an isolated concern. Just below this layer is the mid-February crust/facet/surface hoar layer, which may also still be reactive in isolated areas. Both layers have the potential for wide propagations and large avalanches are still possible.

Problems

Wind Slabs

Recent winds shifted dry new snow into wind slabs on lee and cross loaded slopes. Cornices may be large and fragile.

Be cautious as you transition into wind affected terrain.>Use ridges or ribs to avoid areas of wind loaded snow.>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

2 - 5

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