Avalanche Forecast

Issued: Mar 30th, 2017 3:32PM

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

triley, Avalanche Canada

Northwest Coastal.

The next pulse of snow, rain at lower elevations, and wind is forecast overnight. Expect avalanche danger to increase as the storm slabs deepen.

Summary

Confidence

Moderate - Forecast snowfall amounts are uncertain on Friday

Weather Forecast

Overnight: Cloud developing this evening combined with strong southwest winds and 5-10 cm of new snow by morning. Friday: Overcast with 15-20 cm of new snow above 1000 metres combined with strong southwest winds. Saturday: 15-20 cm of new snow with freezing levels dropping below 1000 metres and winds backing off to moderate southwest. Sunday: Another 5-8 cm of new snow with moderate westerly winds.

Avalanche Summary

Numerous natural storm slabs up to size 2.0 were reported on Wednesday, as well as one natural cornice size 2.0 in the south of the region, and one natural cornice size 3.0 near Stewart. Two natural persistent slab avalanches were reported northwest of Terrace on Tuesday that released down 100 cm and failed in shallow rocky areas adjacent o large slopes.. On Sunday, a machine-triggered Size 3 (with crown approximately 2m thick) was reported in the South Douglas area just north of Terrace on a northwest aspect near 1400m. The slab is suspected to have run on the late February interface and involves an incredible story of survival. Click here for details.

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. The February 21st 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

Forecast new snow and wind are expected to develop or add to existing storm slabs overnight and during the day tomorrow.

Minimize overhead exposure during periods of heavy loading from new snow, wind.If triggered, the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

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

Possible

Expected Size

2 - 3

Loose Wet

Loose wet avalanches may release naturally at lower elevations due to warm daytime temperatures, new snow or rain, and high freezing levels.

Use extra caution on slopes if the snow is moist or wet.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Mar 31st, 2017 2:00PM