Archived

Avalanche Forecast

Feb 16th, 2012–Feb 17th, 2012

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

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

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

Regions: Purcells.

Confidence

Fair - Forecast snowfall amounts are uncertain on Saturday

Weather Forecast

Overnight snowfall is expected to total about 2-5 cm in most of the region. Another ridge is forecast for Friday that should bring mostly clear skies and light winds during the day. The next Pacific frontal system is expected to move inland from the coast during the evening. Moderate snowfall combined with moderate southwest wind is expected during the morning, turning to flurries in the afternoon. Forecast amounts are about 5-10 cm total. Light flurries are expected to continue on Sunday.

Avalanche Summary

A couple of size 3.0 avalanches were reported from the northern Purcells, one that stepped down to the ground around midway down the path. The other avalanche was on a cross loaded slope at about 2100 metres. These were reported as recent, but I am not sure of the occurrence date.

Snowpack Summary

Widespread surface hoar has been buried by a couple of cm of new snow in most of the region. A melt-freeze crust has developed on southerly aspects at all elevations. North and east aspects continue to have dry snow and some surface sloughing in steep terrain. Basal facets have not been reactive, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are suspect locations.

Avalanche Problems

Wind Slabs

Forecast new snow and strong southwest wind are expected to develop windslabs in the alpine and at treeline.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 5

Cornices

Watch for tender cornices at ridge tops. They may be destructive by themselves, and have potential to trigger large avalanches on the slope below.

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

Elevations: Alpine.

Likelihood: Unlikely - Possible

Expected Size: 1 - 5

Deep Persistent Slabs

Although a deep persistent slab would most likely require a large trigger, they are still possible; especially in thin snowpack areas or in unsupported, rocky terrain.

Aspects: All aspects.

Elevations: Alpine.

Likelihood: Unlikely

Expected Size: 3 - 7