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Archived

Avalanche Forecast

Apr 14th, 2018–Apr 15th, 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: Sea To Sky.

Slabs have been reactive to human traffic, particularly in lee terrain features. The likelihood of triggering avalanches will increase if the sun comes out, so best to avoid southerly slopes under intense sun.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

SUNDAY: A mix of sun and cloud, light northeast winds, alpine temperature -4 C, freezing level 1500 m.MONDAY: Cloudy with light snowfall, accumulation 5 to 10 cm, light west winds, alpine temperature -5 C, freezing level 1400 m.TUESDAY: Mostly cloudy, light west winds, alpine temperature -5 C, freezing level 1400 m.

Avalanche Summary

On Friday, many small to large (size 1 to 2) storm and wind slabs were explosively controlled and ski cut across the region.  They were generally at treeline and alpine terrain with slab depths of 20 to 50 cm.  Cornices were also reactive to explosives but were generally small.

Snowpack Summary

30 to 40 cm of new snow between Thursday and Saturday has been redistributed by strong south winds, forming reactive storm and wind slabs up to 1 m deep.  Ridgelines are heavily corniced and if they fail they could trigger slabs on slopes below.A weak layer consisting of surface hoar, facets, and/or a melt-freeze crust from late March is now buried about 60 to 140 cm. This layer is spotty in its distribution but has recently produced large avalanches. It is mostly likely to be problematic on west, north, and east aspects between 1900 m and 2250 m. Below this, the snowpack is well-settled and strong.

Avalanche Problems

Wind Slabs

Recent snow has created new slabs, which are up to 1 m thick in lee features due to strong south winds. Precipitation fell as rain at low elevations, so expect wet snow. Loose wet avalanches are possible if the sun comes out.
Avoid steep slopes when air temperatures are warm or the solar radiation is strong.Use ridges or ribs to avoid pockets of wind-loaded snow.Use extra caution around cornices: they are large, fragile, and can trigger slabs on slopes below.

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

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2.5

Persistent Slabs

A weak layer buried 60 to 140 cm is still surprising people and producing large and destructive avalanches. Be particularly cautious around upper treeline and alpine terrain on shady aspects, where this layer is most likely to be a problem.
Pay attention to overhead hazards like cornices, which could trigger persistent slabs.Be aware of the potential for wide propagation due to the presence of buried weak layers.Avoid steep terrain or areas with a thin or variable snowpack.

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

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 3