Avalanche Forecast

Issued: Jan 2nd, 2017 4:27PM

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

triley, Avalanche Canada

Northwest Coastal.

Expect change to be slow due to cold temperatures. Persistent slab avalanches will continue to be a problem for human triggering.

Summary

Confidence

Moderate -

Weather Forecast

Clear and cold overnight with strong northeast winds. The air in the alpine is expected to be 5-10 degrees warmer than the valleys. Clear and cold on Tuesday with strong northeast winds. Clear and cold on Wednesday with a chance of above freezing temperatures in the alpine. Cloud developing on Thursday with warmer temperatures and a switch to westerly winds.

Avalanche Summary

On Monday, in the north of the region near Ningunsaw a natural size 3.5 was reported that released on basal facets and ran full path. On Sunday, new wind slabs that formed from reverse loading on south aspects were reported to have released naturally up to size 2.5 in the south of the region. In the north, one size 2.0 natural persistent slab was reported that released down to the ground exposing a bed surface of rock slab.

Snowpack Summary

Recent storms deposited 50-80 cm of snow combined with strong winds, most recently from the north. The storm snow overlies a layer of feathery surface hoar (up to 15 mm in sheltered areas) buried on December 25, making wide propagations possible. Ongoing reports indicate this combination of layers is susceptible to easily triggered avalanches, including avalanches running in low angled terrain. An earlier (and therefore deeper) weak interface that formed during the early December cold snap can be found in isolated areas buried 100-150 cm deep. The layer consists of preserved surface hoar or weak faceted (sugary) snow. The lower snowpack is well consolidated in deep snowpack areas. In shallow snowpack areas, especially north of Ningunsaw, an old rain crust near the bottom of the snowpack has developed weak facets and might be triggerable from a thin or rocky area on a convex slope.

Problems

Persistent Slabs

Surface hoar that was buried last week continues to be sensitive to human triggering in the Terrace area. This problem may be more widespread across the southern half of the region. Please submit your observations to the MIN.

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

Likely

Expected Size

2 - 3

Wind Slabs

Forecast extreme northeast winds are expected to shift loose surface snow into stiff new wind slabs in exposed lee terrain. Watch for areas that were previously scoured and may become reverse-loaded as the winds switch direction.

Be cautious as you transition into wind affected terrain.If triggered the wind slabs may step down to deeper layers resulting in large avalanches.Avoid travelling in areas that have been reverse loaded by winds.

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

Elevations: Alpine, Treeline.

Likelihood

Likely

Expected Size

1 - 2

Valid until: Jan 3rd, 2017 2:00PM