Archived

Avalanche Forecast

Feb 1st, 2013–Feb 2nd, 2013

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

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: Kootenay Boundary.

Saturday’s danger ratings are based on intense sunshine and warming affecting the upper snowpack.

Confidence

Fair - Timing or intensity of solar radiation is uncertain on Saturday

Weather Forecast

Saturday: Light W winds. Alpine temperature near +3. Sunny skies, with valley cloud. No snow.Sunday: Moderate SW wind. Alpine temperature near -4. Light snow is possible.Monday: Light SW wind. Alpine temperature near -5. Light snow.

Avalanche Summary

Size 1 to 2 loose dry avalanches have been failing with natural and human triggers in steep terrain. Human-triggered slabs (size 1 to 2) have also been failing on the Jan 23 interface. In many cases, these events have been on wind-loaded aspects.

Snowpack Summary

Recent NW winds have redistributed 15-40 cm of recent snow into soft or hard slabs on lee slopes in the alpine and at treeline. A weak interface buried on Jan 23 seems to be becoming more reactive as the slab above settles and becomes more cohesive. Deeper, about 50-60cm down, a weak interface buried in early January exhibits moderate to hard, sudden results in snowpack tests. The snowpack below this is generally well bonded. Forecast warming may increase the likelihood of triggering a persistent slab.

Avalanche Problems

Wind Slabs

Be alert for wind slabs behind terrain breaks such as ridges and ribs.

Be cautious as you transition into wind affected terrain.>Travel on ridgetops to avoid wind slabs on slopes below.>Cornices become weak with daytime heating, so avoid traveling on exposed slopes.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 4

Persistent Slabs

A mixed bag of weak interfaces is buried about 40 cm down. As temperatures rise, the likelihood of triggering a persistent slab may increase.

Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.>Choose well supported terrain without convexities.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible - Likely

Expected Size: 1 - 4