Archived

Avalanche Forecast

Mar 22nd, 2012–Mar 23rd, 2012

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

3: Considerable

The avalanche danger rating at treeline will be considerable

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

Alpine

3: Considerable

The avalanche danger rating in the alpine will be considerable

Treeline

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

2: Moderate

The avalanche danger rating below treeline will be moderate

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

2: Moderate

The avalanche danger rating below treeline will be moderate

Regions: Sea To Sky.

Confidence

Good

Weather Forecast

Mainly sunny and mild weather is expected through the weekend. The freezing level should be near valley bottom overnight and rise to 1200m Friday and 1500m on Saturday and Sunday. Ridge top winds are generally light from the south.

Avalanche Summary

Recent avalanche activity includes skier and explosive controlled avalanches to Size 1.5 from exposed wind-loaded features. The average depth was around 15-30cm. There were also several cornice failures reported. There was one report of a Size 4 avalanche near Rainbow Mountain (west of Whistler) that occurred during last weeks storm cycle. It was an impressive slide that destroyed a significant amount of mature forest.

Snowpack Summary

Solar aspects are likely going through a melt-freeze cycle with frozen snow overnight becoming moist through the day. Snow and wind created fresh wind slabs and storm slabs on Tuesday. Heavy snow which fell last week is settling, but variable storm snow weaknesses and buried crusts mean a deep storm slab release is still possible. Cornices are large and threaten slopes below. A persistent weakness, formed in mid-February, continues to produce hard, sudden planar results in snowpack tests. The likelihood of triggering this layer has gone down, but very large avalanches remain possible, which could be triggered by a shallower avalanche or cornice fall. The snowpack depth at treeline is 350-500cm.

Avalanche Problems

Wind Slabs

Wind slabs lurk below ridges, behind terrain features and in gullies. They may be buried by new snow, making them hard to spot.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Loose Wet

Loose wet avalanches are likely on steep sun-exposed slopes during the day. There is potential for these heavy wet slides to step down to deeper weaknesses and create a large slab avalanche.

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

Elevations: All elevations.

Likelihood: Likely - Very Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Persistent weaknesses still have the potential to create very large, destructive avalanches if triggered. Possible triggering mechanisms include a person/sled on a thin snowpack spot, cornice fall, or step-down avalanche.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 8