Avalanche Forecast

Issued: Mar 5th, 2013 8:20AM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Loose Wet, Wind Slabs and Cornices.

pmarshall, Avalanche Canada

Northwest Coastal.

Summary

Confidence

Good

Weather Forecast

Synopsis: A ridge of high pressure will maintain mostly sunny skies for the next few days. Wednesday and Thursday: The freezing level should rise to around 1000-1200 m during the day and drop back to valley bottom overnight. Outflow winds should ease off by Wednesday and we should generally see light winds from the north. Friday: Freezing levels could climb to 2000 m during the day on Friday.

Avalanche Summary

Recent reports include a few small natural wind slabs in steep lee terrain in response to northerly outflow winds. A few natural cornice failures, ice falls, and glide slab releases have also been reported. One cornice fall observed just north of Terrace triggered a size 3 slab avalanche that is suspected to have released on the late February weak layer. This event could have been a few days old.

Snowpack Summary

Outflow winds (from the north and east) have create new hard and soft wind slabs in exposed lee terrain. In sheltered areas the snow surface consists of facets, surface hoar, or a sun crust/ moist snow on south facing slopes. A layer of surface hoar, facets and/or a crust is buried down 50-90 cm, but most operators report a good bond at this interface. Watch out for cornices, as they are large and fragile. Several large cornice falls have been reported over the past few days. Most have not triggered slabs on the slopes below, however at least one triggered a very large avalanche. The mid snowpack layers are generally well settled and strong. Facets at the base of the snowpack have resurfaced as a concern now that spring is on the doorstep and full-depth releases are becoming more likely (primarily in the northern part of the region).

Problems

Loose Wet

Warm sun is weakening surface snow, particularly on steep south-facing slopes. Loose wet avalanches can entrain a surprising amount of mass as they travel.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.>Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>

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

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 3

Wind Slabs

Outflow winds have produced thin new wind slabs behind terrain breaks, primarily on southwest to northwest aspects on Tuesday.

Avoid travelling in areas that have been reverse loaded by winds.>Be cautious as you transition into wind affected terrain.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 3

Cornices

Cornices may fail naturally with daytime warming and sunshine this week. These could potentially trigger a slab on the slope below.

Give cornices a wide berth when travelling on or below ridges.>Do not travel on slopes that are exposed to cornices overhead.>

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 6

Valid until: Mar 6th, 2013 2:00PM