Avalanche Forecast

Issued: Jan 7th, 2017 4:13PM

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

shorton, Avalanche Canada

Northwest Coastal.

Increasing outflow winds will transport new snow and maintain dangerous avalanche conditions.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SUNDAY: Sunny, moderate east winds increasing to strong overnight, alpine temperatures around -15.MONDAY: Cloudy with scattered flurries and accumulations of 5 cm, strong outflow (east) winds, alpine temperatures around -10.TUESDAY: Sunny, strong to extreme outflow (east) winds, alpine temperatures around -15.

Avalanche Summary

On Saturday, poor visibility limited avalanche reports to a few size 1 natural avalanches at low elevations, but larger storm slab avalanches likely occurred at higher elevations. Large persistent slab avalanches have been reported on a regular basis in the Ningunsaw area for the past few weeks.On Sunday, increasing winds will transport the recent storm snow and continue to build touchy storms slabs. Triggering larger persistent slab avalanches on buried surface hoar layers remains possible.

Snowpack Summary

20-50 cm of new storm snow sits above a variable interface composed of hard wind slabs, weak surface hoar, and faceted snow. Expect the new snow to bond poorly to this interface and form extra touchy storm slabs on wind-loaded features. Wind-loading will likely occur on a wide variety of aspects, as winds are shifting to the northeast. Below the new snow, a well settled slab sits above the Christmas surface hoar layer, which is now buried 50-100 cm deep and may still be reactive in sheltered areas. Deeper weak layers have only been reactive in areas with thin snowpacks. This includes a facet layer from mid-December that has been reactive in snowpack tests at lower elevations, and weak facets near the ground that have produced avalanches in the northern part of the region.

Problems

Storm Slabs

Strong outflow winds will continue to build touchy slabs that sit above a variety of weak layers including surface hoar.

Avoid travelling in areas that have been reverse loaded by winds.Be cautious as you transition into wind affected terrain.Use caution on open slopes and convex rolls

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Persistent Slabs

Weak layers of buried surface hoar up to a metre deep may be 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 - 3

Valid until: Jan 8th, 2017 2:00PM