Archived

Avalanche Forecast

Feb 22nd, 2018–Feb 23rd, 2018

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.

Watch for wind slabs on a variety of slopes at treeline and alpine elevations.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Friday

Weather Forecast

FRIDAY: 2-10 cm snow. Freezing level near 500 m. Moderate to strong westerly winds. SATURDAY: Light snow. Freezing level near 300 m. Moderate winds. SUNDAY: Flurries. Freezing level near 600 m. Moderate winds.More details can be found in the Mountain Weather Forecast.

Avalanche Summary

Rapid wind loading caused a natural avalanche cycle to size 2.5 on Wednesday. With ongoing moderate to strong winds forecast, wind slabs will remain possible to trigger over the next few days. Persistent slabs could still be triggered from thin-to-thick snowpack areas, or with a heavy load like a cornice fall.

Snowpack Summary

The snowpack has gone through several bouts of fighting with strong to extreme northerly winds in the last week. You are likely to encounter wind slabs in many places. Variable surface conditions include fragile cornices, hard and soft wind slabs, and scoured surfaces. The wind slabs sit on various old surfaces including sun crusts, facets and spotty surface hoar (which is most prevalent in sheltered treed locations). Around 50-150 cm down, you will find a crust/surface hoar layer from mid-January, which still has the chance to surprise you and could be triggered from a thin snowpack spot, or with a large trigger like cornice fall. Facets at the base of the snowpack can possibly be triggered from shallow snowpack areas.

Avalanche Problems

Wind Slabs

Wind slabs are widespread and could be triggered by the weight of a person.

Travel on ridgetops to avoid wind slabs on slopes below.Give cornices a wide berth when travelling on or below ridges.Be cautious as you transition into wind affected terrain.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2.5

Persistent Slabs

Buried weak layers are most likely to be triggered from thin or variable depth snowpack areas; or with a large load like a cornice fall.

Avoid thin, rocky or sparsely-treed slopes.If triggered the storm/wind slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Unlikely - Possible

Expected Size: 1.5 - 3.5