Avalanche Forecast

Issued: Apr 1st, 2017 3:34PM

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

Avalanche Canada triley, Avalanche Canada

Storm slabs may continue to be reactive due to the forecast new snow and wind overnight. Avalanche danger will trend down with forecast cooling in the next few days.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Sunday

Weather Forecast

Overnight: 5-10 cm of new snow with freezing levels down to 400 metres, and moderate west winds. Sunday: Cloudy and unsettled with a chance of convective flurries. Daytime freezing level up to 800 metres. Monday: Overnight freeze down to 500 metres followed by mostly sunny skies and light winds. Tuesday: Overcast with light snow and increasing southerly winds.

Avalanche Summary

On Friday we had one report of a loose wet avalanche size 1.0 that released from a ski cut below treeline in the Shames area. One natural ice fall and one natural cornice fall size 3.0 were reported from the Bear Pass area on Thursday. Numerous natural storm slabs up to size 2.0 were reported on Wednesday. I suspect that storm slabs were active on Saturday due to the combination of new snow, warm temperatures, and moderate to strong winds.

Snowpack Summary

Storm slabs continue to develop in the alpine and at treeline. Warm daytime temperatures have created moist snow at treeline and wet snow below treeline. In the Shames area on Friday there was 12 cm of moist storm snow above the most recent melt-freeze crust. The top 40-60 cm of the snowpack at 1200 metres was reported to be moist, and the late February layer was down 118 cm producing moderate sudden collapse shears. The late February persistent weak layer continues to be a concern for triggering large avalanches. This combination of crust and weak facets is now down 100-150 cm, and may be triggered by light additional loads in shallow weak spots adjacent to large terrain features. The snow below treeline may become weak and release as loose wet avalanches or wet slabs in steep unsupported terrain features.

Problems

Storm Slabs

An icon showing Storm Slabs
Storm slabs may continue to be touchy with the forecast new snow and wind.
If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

An icon showing Persistent Slabs
A weak facet/crust layer from late February has produced several large human triggered avalanches the past few days. Triggering this layer is most likely in shallower areas, but a storm slab or cornice fall could act as a trigger.
Avoid steep convexities or areas with a thin or variable snowpack.Use conservative route selection, choose moderate angled and supported terrain with low consequence.Remote triggering is a concern, watch out for adjacent slopes.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Unlikely - Possible

Expected Size

2 - 3

Valid until: Apr 2nd, 2017 2:00PM