Avalanche Forecast

Issued: Mar 31st, 2017 4:37PM

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

cgarritty, Avalanche Canada

Cariboos.

Forecast wind and light snowfall will see wind slabs and cornices continue to grow. The potential for one of these to release and trigger a deeper persistent slab remains a real concern for Saturday.

Summary

Confidence

Moderate -

Weather Forecast

Friday night: Flurries bringing approximately 5 cm of new snow. Moderate to strong south winds.Saturday: Mainly cloudy with continuing flurries bringing approximately 5 cm of new snow. Moderate to strong west winds. Freezing level to 1700 metres with alpine temperatures around -4.Sunday: Mainly cloudy with scattered flurries bringing up to 5 cm of new snow. Light to moderate northwest winds. Freezing level to 1500 metres with alpine temperatures around -7.Monday: A mix of sun and cloud with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1600 metres with alpine temperatures around -7.

Avalanche Summary

Reports from Thursday included observations of two large (Size 2.5 and Size 3) storm slabs releasing naturally from steep alpine terrain north of Blue River. Crown fractures of these slides ranged from 60-80 cm. Extensive natural sluffing to Size 2 was also observed, with loose dry activity on northerly aspects and loose wet from solar aspects. One Size 1 cornice fall was also reported.

Snowpack Summary

Up to 40 cm of recent storm snow has fallen at upper elevations. The new snow is dry up high and moist from 1800 m and below. This now brings 40-90 cm of accumulated snow which overlies a rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 120-150 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a real concern while touchier wind slabs, storm slabs and cornices continue to present the risk of acting as triggers for deeper weaknesses.

Problems

Wind Slabs

Recent southwest winds have redistributed storm snow in exposed terrain at higher elevations, forming large and reactive wind slabs. Cornices have also grown large and may become weak with daytime warming or during stormy periods.

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.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

A cornice fall or smaller slab avalanches could trigger large, destructive avalanches on deeply buried weak layers. There is a low likelihood of triggering but a high consequence if triggered. These avalanches would likely run full path.

If triggered, wind slabs or cornices may step down to deeper layers resulting in large avalanches.Avoid lingering in runout zones.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Unlikely - Possible

Expected Size

2 - 4

Loose Wet

Daytime warming and rain will deteriorate the snowpack below treeline on Saturday. This has the potential to initiate loose wet avalanches that may slide easily on a buried crust.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Apr 1st, 2017 2:00PM