Archived

Avalanche Forecast

Feb 19th, 2012–Feb 20th, 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

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

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

3: Considerable

The avalanche danger rating below treeline will be considerable

Regions: Kootenay Boundary.

Check out the recent Forecaster Blog post discussing the "Tipping Point".

Confidence

Fair - Intensity of incoming weather is uncertain on Tuesday

Weather Forecast

Monday: flurries bringing minimal accumulation of new snow. Light to moderate NW winds. Freezing level around 800 m. Tuesday: 5-10 cm new snow with winds increasing moderate to strong from the NW. Freezing level rising to 1000 m. Tuesday night into Wednesday: a slightly stronger band of moisture arrives bringing 10-15 cm new snow, freezing levels rising to 1500 m and strong westerly winds.

Avalanche Summary

Snow amounts over the early Feb weak layer reached threshold in many places on Saturday. Natural avalanches were observed in the storm snow to size 1.5. Avalanche control at Kootenay Pass produced avalanches up to size 2 running on a crust buried around 35 cm below the surface. Read the forecaster blog for further discussion on reaching the "tipping point".

Snowpack Summary

Saturday's storm brought around 15 cm new snow, bringing the gradually incrementing snow amounts above the early Feburary surface hoar layer to around 30 cm. Alpine winds have been strong enough to blow snow around and touchy wind slabs have formed predominantly on northerly and easterly aspects. The early February weak layer comprises large surface hoar on sheltered aspects, facets on northerly aspects and a crust on solar aspects. In shallow snowpack areas concerns remain for the mid-December persistent weakness down around 80-100cm and for basal facets. Treeline snowpack depths are approximately 230 cm.

Avalanche Problems

Persistent Slabs

A persistent weak layer comprising surface hoar in sheltered areas, a crust on solar aspects and facets elsewhere lies buried 20-30 cm below the surface. I has been reacting to human triggers, producing avalanches up to size 2.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 4

Wind Slabs

New thin wind slabs have developed on exposed lee terrain. The underlying snow surface makes a poor bond to newly forming wind slabs.

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Deep Persistent Slabs

Large avalanches remain a concern in shallow rocky areas where they could be triggered with a very heavy load, such as cornice fall.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 3 - 7