Archived

Avalanche Forecast

Mar 4th, 2013–Mar 5th, 2013

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Alpine

2: Moderate

The avalanche danger rating in the alpine will be moderate

Treeline

1: Low

The avalanche danger rating at treeline will be low

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Coastal.

Confidence

Fair

Weather Forecast

Synopsis: A ridge of high pressure will maintain mostly sunny skies for the next few days. The freezing level should rise to around 1000-1200 m during the day and drop back to valley bottom overnight. Ridgetop winds could be in the moderate to strong range from the east on Tuesday, but will ease off to light from the northwest for Wednesday and Thursday.

Avalanche Summary

Sunshine and warming have triggered loose avalanches and cornice failures over the last couple of days. An explosive triggered cornice in the Bear Pass area on Sunday did trigger a size 2.5 slab on the slope below. This slab failed within the latest storm snow and showed limited propagation.

Snowpack Summary

About 40-70 cm recent storm snow is showing signs of stabilizing. Recent strong, variable winds left wind slabs at treeline and alpine elevations. Direct sun is weakening the snowpack on sunny aspects during the day. A layer of surface hoar, facets and/or a crust is buried in the upper snowpack, but most operators report a good bond at this interface. Watch out for cornices, as they are large and fragile. Some 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.

Avalanche 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.

Watch for wet loose or slab activity with forecast rain and/or warm temperatures.>Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Wind Slabs

Thin new wind slabs may be found behind terrain breaks, primarily on southwest to northwest aspects on Tuesday. .

Be cautious as you transition into wind affected terrain.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3

Cornices

Cornices may fail naturally with daytime warming and sunshine this week.

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 - Likely

Expected Size: 2 - 5