Avalanche Forecast

Issued: Apr 17th, 2017 4:31PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs, Cornices and Loose Wet.

mgrist, Avalanche Canada

Sea To Sky.

Wind slabs and cornices are the main concerns right now. Carefully assess terrain before committing to bigger lines.

Summary

Confidence

Moderate - Intensity of incoming weather systems is uncertain

Weather Forecast

We're looking at unsettled and variably wet spring weather throughout the forecast period. TUESDAY: Wet snow Monday overnight through Tuesday (10-20cm by Tuesday afternoon). Freezing level around 1600 m. Winds moderate southwesterly.WEDNESDAY: More wet snow (10-15cm) above 1500m. Winds strong southerly.THURSDAY: Flurries continue (5-10cm) with snow above 1600m. Winds 20-30 km/h from the south.

Avalanche Summary

On Monday we had preliminary reports of an avalanche involvement in the Tantalus range near 2000m, aspect not known. All in the party got out safely.On Sunday, skiers triggered a Size 1.5 slab avalanche in a northwest facing couloir in the alpine near Whistler. See here for their MIN report. On Saturday, skiers triggered a Size 1.5 wind slab on the Spearhead traverse near Fissile, on a southwest aspect. See here for more details.

Snowpack Summary

Late last week we had 20-30 cm of settling storm snow above 1500m. Pockets of reactive wind slab (5-40cm thick) can still be found in the alpine and exposed features at treeline - this has surprised skiers throughout the long weekend (see Avalanche Summary above). Warm temperatures on Sunday (+5 at treeline) resulted in a melt-freeze crust on most aspects and elevations at treeline and below. Cornices remain large in some areas and could trigger large avalanches when they fail. The fatal accident near Lions Bay a week ago illustrates the danger of cornices breaking off, and the large avalanches they can trigger.

Problems

Wind Slabs

Isolated wind slabs may still be lingering in the alpine and near exposed treeline features.

Be cautious as you transition into wind affected terrain.Use ridges or ribs to avoid pockets of wind loaded snow.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Cornices

Where they exist, cornices pose a significant hazard and should be avoided.

Falling cornices can trigger large avalanches.Give cornices a wide berth when travelling on or below ridges.Extra caution needed around cornices with current conditions.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

2 - 3

Loose Wet

Loose wet avalanches are more likely at lower elevations where the snowpack may be isothermal and precipitation falls as rain. Even small slides can have serious consequences.

Avoid exposure to terrain traps where the consequences of a small avalanche could be serious.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Apr 18th, 2017 2:00PM