Archived

Avalanche Forecast

Feb 11th, 2013–Feb 12th, 2013

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

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

2: Moderate

The avalanche danger rating at treeline will be moderate

Below Treeline

1: Low

The avalanche danger rating below treeline will be low

Regions: Northwest Inland.

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Synopsis: A frontal system is moving across the area bringing light snowfall Monday night and into Tuesday. By Wednesday, a ridge of high pressure sets up, which should hold until Thursday afternoon.Monday night: 2-5 cm new snow overnight with strong SW winds and freezing level around 700m.Tuesday: Around 5 cm new snow, with strong to extreme SW winds gusting to 80km/h at ridgetop. Freezing level around 1100m.Wednesday: Dry and sunny. Freezing level falling to valley bottom. Moderate NW winds in the morning, diminishing through the day.Thursday: Dry, with cloud increasing through the day. SW winds starting light, increasing to moderate through the day.

Avalanche Summary

Loose snow avalanches were reported during the recent warm weather.

Snowpack Summary

Around 20-40cm recent new snow sits on a variety of old surfaces, which vary from facets to crusts and isolated pockets of surface hoar (sheltered treeline and below treeline). There is very limited information about the nature of the interface, with the only results suggesting reactivity in sheltered, shady treeline and below treeline slopes (preserved surface hoar). I would stress the importance of digging down to find and test weak layers.A strong mid-pack currently overlies a weak base layer of facets/depth hoar. It is worth noting that the snowpack in general is quite shallow compared to averages; triggering the basal weakness may still be possible from thin spots, rocky outcrops or under the weight of larger triggers such as cornice fall.

Avalanche Problems

Wind Slabs

New snow and shifting winds have built wind slabs that are likely found behind terrain breaks such as ridges and ribs. Watch for katabatic winds descending from glaciers.

Avoid freshly wind loaded features.>Highmark or enter your line well below ridge crests to avoid wind loaded pillows.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 4

Persistent Slabs

Buried beneath the new snow sits a surface hoar/crust/facet weakness. This may be sensitive to rider triggers in steeper sheltered terrain or over convex rolls, especially at treeline and below treeline elevations.

Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 6