Archived

Avalanche Forecast

Mar 11th, 2018–Mar 12th, 2018

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

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

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.

Expect avalanche danger to increase as the temperature rises through the day. Danger ratings are rated for the heat of the day when the likelihood of triggering an avalanche is highest.

Confidence

Moderate - Freezing levels are uncertain on Monday

Weather Forecast

MONDAY: Mix of sun and cloud / Light south wind / Alpine temperature 4 / Freezing level 2100m TUESDAY: Mix of sun and cloud / Moderate south wind / Alpine temperature 6 / Freezing level 2600m WEDNESDAY: Mainly cloudy with isolated flurries or rain showers / light southwest wind / Alpine temperature 6 / Freezing level 1500m

Avalanche Summary

On Friday reports indicate numerous size 2-2.5 natural and explosive controlled storm snow avalanches running on all aspects in the alpine and at tree line. There were also several skier triggered storm slab avalanche size 1.5-2 both Friday and Saturday on north aspects in the alpine and tree line. Expect to see a rise in solar triggered storm slab and loose wet avalanche activity in the coming days with clear skies and high freezing levels.

Snowpack Summary

Friday's new snow has settled and been redistributed by predominantly west and southwest wind and sits on mostly unconsolidated snow from last week and on a sun crust on south-facing slopes. On sheltered northerly aspects it may also be sitting on a layer of surface hoar.A mix of weak layers exist 50-100 cm below the surface, including small surface hoar on shady aspects and a crust on solar aspects. These layers have consistently been reactive in snowpack tests, suggesting they could potentially remain reactive to human triggers as well. Deeper weak layers that formed in January and December have gained strength and gone dormant at this time. They include several surface hoar and facet layers 1 to 2 m below the surface and a crust/ facet interface near the base of the snowpack.

Avalanche Problems

Loose Wet

Surface crusts on sun exposed slopes will break down quickly in the heat of the day. Expect to see the surface snow sluff and gather mass in steep terrain as the day warms up.

Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.

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

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 2

Wind Slabs

Fresh storm and wind slabs have formed with recent new snow and moderate southwesterly wind.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Extra caution needed around cornices with current conditions.Be cautious as you transition into wind affected terrain.

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2

Persistent Slabs

Weak layers exist 40-100 cm below the surface, including surface hoar on north-facing terrain and sun crusts on south-facing terrain. These layers may become reactive with the weight of new snow and warming.

If triggered smaller avalanches may step down to deeper layers resulting in large avalanches.Be cautious on convex rolls at and below treeline where buried surface hoar may be preserved.Avoid convexities or areas with a thin or variable snowpack.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Possible

Expected Size: 1.5 - 3