Avalanche Forecast

Issued: Jan 3rd, 2017 4:20PM

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

Avalanche Canada cgarritty, Avalanche Canada

Recently formed wind slabs may become reactive with solar radiation on Wednesday. Keep an eye on the sun and analyze each slope for patterns of wind effect before choosing your line.

Summary

Confidence

High - The weather pattern is stable

Weather Forecast

Wednesday: A mix of sun and cloud with no new snow. Winds moderate from the northeast. Possible alpine temperature inversion bringing alpine temperatures to -5.Thursday: Mainly cloudy with no new snow. Winds light from the west. Alpine temperatures of -6.Friday: Mainly cloudy with scattered flurries bringing up to 5cm of new snow. Winds moderate from the southwest. Alpine temperatures to -8.

Avalanche Summary

Two natural Size 1.5 wind slab avalanches with 40cm deep crowns were observed occurring southwest of Whistler on Monday on steep southwest and southeast slopes. Explosives testing in the Whistler area on Monday successfully targeted several reverse loaded pockets of wind slab in the alpine to Size 1.

Snowpack Summary

Between Monday and Friday last week, 70-100 cm of storm snow accumulated in the region. The critical part of snowpack analysis under current conditions is figuring out how the wind is redistributing this snow into wind slabs. Recent extreme northerly winds have "reverse loaded" much of the new snow onto southerly slopes that were previously scoured. Moderate northerly winds continued to promote this wind slab formation into Tuesday. The existence of wind slabs on solar aspects is important to note as clear skies will allow for strong solar radiation to affect these aspects. Below the new snow from last week lies the Boxing Day interface which consists of wind affected surfaces, faceted (sugary) snow, or surface hoar. Recent observations suggest the overlying snow is generally well bonded to this interface. The mid-December interface is now down 100-150 cm and is generally considered to be stable in this region. Snowpack layers below this are well bonded.

Problems

Wind Slabs

An icon showing Wind Slabs
Wind slabs formed on mainly southwest to east aspect slopes in response to recent extreme northerly winds. Slabs found on south aspect slopes could become more unstable when the sun is out.
Minimize exposure to steep, sun exposed slopes when the solar radiation is strong.Carefully evaluate steep lines for wind slabUse safe ski cutting techniques before entering steep lines.

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

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Jan 4th, 2017 2:00PM