Avalanche Forecast

Issued: Jan 10th, 2017 4:24PM

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

mgrist, Avalanche Canada

Northwest Coastal.

Strong northeast winds will transport snow and maintain dangerous avalanche conditions.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

The strong outflow (northeasterly) winds will decrease on Wednesday. No precipitation is expected until late Thursday, with below average temperatures until then. WEDNESDAY: Sunny. Winds easing to light northwesterly (10-15 Km/hr). Alpine temperatures around -15 Celcius.THURSDAY: Increasing clouds throughout the day. Moderate to strong (south) westerly winds (35-50Km/hr). Alpine temperatures warming to -12 Celcius.FRIDAY: Snow returns with 15-20cm forecast. Strong (60Km/hr) south winds at ridgetop. Alpine highs to -5 Celcius.

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, especially on westerly aspects. Reports from social media show touchy windslabs in the Sterling area, southwest aspect.https://www.facebook.com/groups/314113201944133/permalink/1329849827037127/Another natural persistent slab avalanche was reported in the Ningunsaw area last Thursday, indicating that the persistent problem will linger for some time in the northern part of the region.

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 and is 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 winds will continue to build touchy slabs that sit above a variety of weak layers including the Jan 5/6 surface hoar layer.

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

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

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

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

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Possible

Expected Size

2 - 4

Valid until: Jan 11th, 2017 2:00PM