Avalanche Forecast

Issued: Mar 22nd, 2012 4:00PM

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

pmarshall, Avalanche Canada

Sea To Sky.

Summary

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.

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

Valid until: Mar 23rd, 2012 9:00AM