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Archived

Avalanche Forecast

Feb 19th, 2019–Feb 20th, 2019
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
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
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.

An unusual weak layer makes steep and convex terrain features particularly dangerous.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Some flurries, but clearing after midnight.WEDNESDAY: Dry with sunny breaks. Freezing level rising to around 1000 m in the afternoon. Light northeasterly winds.THURSDAY: Dry and sunny. Freezing level around 700 m. Light northeasterly winds.FRIDAY: 10-15 cm new snow expected. Freezing level around 500 m. Moderate to strong southwesterly winds.

Avalanche Summary

On Monday, search and rescue responded to an avalanche in the Mount Seymour backcountry. The avalanche occurred on a steep feature at treeline elevation (see photo here). Avalanche professionals involved in the rescue indicated wide propagation consistent with a persistent slab problem. The crown depth was variable - 40 to 100 cm, indicating there was wind loading in that area.On Friday and over the weekend, there is evidence of a widespread avalanche cycle up to size 2.5. These avalanches showed impressive propagation, with some being triggered remotely (from a distance) and some occasions stepping down to a 50 cm deep crust layer.

Snowpack Summary

30-50 cm of recent storm snow lies above a crust. The new snow has bonded poorly to this crust and natural and human-triggered avalanche have been noted on this interface. The reactivity of this layer appears to be worse in the south of the region (i.e. the North Shore Mountains) that have seen more snow. Unusually for this region, we expect this layer to remain reactive for some time into the future. New sun crusts may be found near the surface of south-facing aspects, while wind slabs may be found in exposed terrain. The lower snowpack is settled and strong.

Avalanche Problems

Persistent Slabs

There is a weak layer of facets over a crust buried approximately 50 cm below the surface. Persistent slab problems are unusual for this region. Cautious terrain selection is needed to remain safe.
Avoid travel on steep slopes and convex rolls.Be aware of the potential for wide propagations due to the presence of a buried weak layer.

Aspects: All aspects.

Elevations: Treeline, Below Treeline.

Likelihood: Likely

Expected Size: 1.5 - 2.5

Wind Slabs

30-50 cm of recent storm snow may be poorly bonded to crusts.
The new snow may require several days to settle and stabilize.Use caution on open slopes and convex rolls Use caution above cliffs and terrain traps where small avalanches may have severe consequences.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 2