Avalanche Forecast

Issued: Jan 11th, 2017 5:23PM

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

cgarritty, Avalanche Canada

Northwest Coastal.

A complex pattern of wind slabs has developed at higher elevations. Below it, a persistent slab is waiting for the right trigger.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

Thursday: Cloudy with isolated flurries and a trace of new snow in the south of the region. Scattered flurries and up to 5cm in the north. Winds moderate to strong from the southwest. Alpine temperatures to -5, -10 in the north of the region.Friday: Flurries bringing approximately 15 cm of new snow. Winds strong from the southwest. Alpine temperatures around -5.Saturday: 15-30 cm of new snow, with higher amounts in the north of the region. Winds strong to extreme from the southwest. Freezing level rising to 1200 metres with Alpine temperatures around -3.

Avalanche Summary

Over the past few days we've had several reports of natural and human-triggered windslabs (mostly Size 2) in all areas of the region, and especially on westerly aspects. Reports from social media show touchy windslabs on a southwest aspect in the Sterling area.https://www.facebook.com/groups/314113201944133/permalink/1329849827037127/

Snowpack Summary

Recent strong winds (southeast through northeast) have redistributed the 20-40 cm of snow from Friday-Saturday at all elevation bands. This snow sits on a variable interface composed of hard wind slabs, weak surface hoar (Jan 5/6 layer) and faceted snow. The net result is touchy slabs on wind-loaded features that are giving easy to moderate sudden results in snowpack tests. Below the new snow, a well settled slab sits above the Christmas surface hoar layer which is well preserved in southern areas. This surface hoar is now buried 60-100 cm deep, and is still reactive in sheltered areas and steep open features at and below treeline. Deeper weak layers have only been reactive in areas with thin snowpacks. This includes a facet layer from early December that has been reactive in snowpack tests at lower elevations in the southern part of the region, and weak facets near the ground that have produced avalanches in the northern part of the region.

Problems

Wind Slabs

Strong northeast through southeast winds have built touchy slabs above a variety of weak layers. Skillful routefinding will be required to navigate around these slabs at treeline and above.

Be cautious as you transition into wind affected terrain.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Be alert to conditions that change with aspect and elevation.

Aspects: North, North East, East, South East, South, South West.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 3

Persistent Slabs

Weak layers of surface hoar are now buried up to 1.2 metres deep and may be more reactive after the recent loading. Take extra care to avoid thin trigger points and exposure to overhead hazard.

Be aware of the potential for large avalanches due to the presence of buried surface hoar.Use conservative route selection, stick to moderate angled terrain with low consequence.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Jan 12th, 2017 2:00PM