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Archived

Avalanche Forecast

Mar 11th, 2019–Mar 12th, 2019
Alpine
4: High
The avalanche danger rating in the alpine will be high
Treeline
4: High
The avalanche danger rating at treeline will be high
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
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
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: South Coast.

Avoid avalanche terrain on Tuesday. The new snow will need time to settle and gain strength.

Confidence

High -

Weather Forecast

MONDAY NIGHT: Heavy snowfall with accumulations of 20-30 cm, 30-60 km/h southwest wind, treeline temperatures around -2 C, freezing level around 500 m.TUESDAY: Snow continues in the morning with another 5-10 cm then eases off in the afternoon, total accumulation of 30-45 cm over the course of the storm, 20-30 km/h northwest wind as the storm eases, treeline temperatures near -2 C, freezing level 800 m.WEDNESDAY: Mix of sun and cloud, light northwest wind, treeline temperatures near -2 C, freezing level 800 m.THURSDAY: Cloudy with isolated flurries, 30-50 km/h southwest wind, treeline temperatures near +1 C, freezing level 1200 m.

Avalanche Summary

Avalanche activity over the weekend was limited to small slab and loose avalanches in the top 20 cm of snow (size 1). Looking ahead, the most likely problem will be fresh storm slabs, however the lingering persistent weak layer in the North Shore Mountains still poses a low likelihood - high consequence problem.

Snowpack Summary

30-45 cm of new snow will be accompanied with strong southwest wind. The new snow is falling on a sun crust on steep southerly slopes, and possibly on weak surface hoar crystals on sheltered and shaded slopes. The combination will form very touchy storm slabs on Tuesday.A layer of weak and sugary faceted grains sits on a melt-freeze crust about 50 to 120 cm deep. The layer is likely most prominent in the North Shore Mountains and on north aspects. This layer continues to be reactive in snowpack tests. The problem is not typical for the region and we expect this persistent weak layer to continue to linger.The lower snowpack is generally strong.

Avalanche Problems

Storm Slabs

A natural avalanche cycle is expected to start on Monday night and human triggered storm slabs will remain very likely on Tuesday.
Avoid avalanche terrain during periods of heavy loading from new snow and wind.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.Be aware of the potential for wide propagations.

Aspects: All aspects.

Elevations: All elevations.

Likelihood: Very Likely

Expected Size: 1 - 2

Persistent Slabs

A weak layer is buried 50 to 120 cm deep in the North Shore Mountains. The layer consists of weak faceted grains above a crust. This layer could become reactive with the additional load of the new snow.
Avoid exposure to overhead avalanche terrain, large avalanches may reach the end of run out zones.Storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3