Avalanche Forecast

Issued: Jan 9th, 2017 4:19PM

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

mgrist, Avalanche Canada

Northwest Coastal.

Arctic outflow again! Strong northeast winds will transport new snow and maintain dangerous avalanche conditions.

Summary

Confidence

Moderate - Due to the number of field observations

Weather Forecast

The main story is the strong northeasterly winds forecast for Tuesday. No precipitation is expected until late Thursday, with below average temperatures until then. TUESDAY: Sunny. Strong outflow (northeast) winds, Alpine temperatures around -15. WEDNESDAY: Sunny. Winds easing to light northwesterly. Alpine temperatures around -15. THURSDAY: Increasing clouds in the afternoon. Moderate westerly winds. Alpine temperatures warming slightly to -13.

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 on Thursday, indicating that the persistent problem will linger for some time in the northern part of the region.

Snowpack Summary

Recent winds 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, 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 40-80 cm deep, and is still reactive in sheltered areas. 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 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: North, North East, East, South East, South.

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 3

Persistent Slabs

Weak layers of buried surface hoar up to 1.5 metres 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 - 4

Valid until: Jan 10th, 2017 2:00PM