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Avalanche Forecast

Jan 25th, 2016–Jan 26th, 2016
Alpine
3: Considerable
Treeline
3: Considerable
Below Treeline
2: Moderate
Alpine
4: High
Treeline
3: Considerable
Below Treeline
2: Moderate
Alpine
4: High
Treeline
3: Considerable
Below Treeline
2: Moderate

Regions: Sea To Sky.

If more than 20 cm of new snow falls on Tuesday, the Avalanche Danger may be HIGH in the alpine.

Confidence

Moderate - Intensity of incoming weather systems is uncertain on Tuesday

Weather Forecast

Between 10-15cm of new snow is expected for the Whistler are on Tuesday with up to 25cm of snow possible in the south and western portions of the region. Winds will be strong and southwesterly with freezing levels at about 1700m. On Wednesday 20cm of wet snow is expected with strong southwest winds and freezing levels hovering at about 2200m.

Avalanche Summary

Explosives control on Sunday produced a few cornice collapses to size 2. An explosive charge also triggered a size 2 persistent slab avalanche on an adjacent alpine slope where buried surface hoar was lingering. There were also a few human involvements on Sunday. A snowboarder got too close to a recently formed cornice and triggered a size 2 cornice fall. The individual was not injured in the event. Of note, a size 1.5 persistent slab avalanche was also reported on Disease Ridge in the Spearhead Range. An individual was partially buried in the event, but was assisted quickly by their party. Looking forward, a warm, wet weather system is expected to spark a new round of wind slab activity in high elevation lee terrain, but warm temperatures and loading will also increase the likelihood of waking up any lingering persistent weaknesses that were not triggered by last week's storm.

Snowpack Summary

The "Pineapple Express Light" dumped 80-160 mm of precipitation on the South Coast this week. Most of this fell as snow above 1800-2000 m (over 1 m) with mixed rain and snow or just heavy rain below 1800 m. Heavy snow and strong winds have formed deep and dense wind slabs in exposed lee terrain and caused substantial cornice growth. Expect to find a rain crust at or near the surface (below 10-20 cm of fresh snow) at lower elevations. In many areas, the early and mid-January surface hoar layers may have been wiped-out by the storm and subsequent avalanche cycle; however, recent Mountain Information Network observations from the Spearhead range show this layer is still producing "sudden" test results. These layers would be down between 80 and 150 cm deep, and still have the capacity to surprise with nasty consequences. The mid and lower snowpack is generally strong, with the exception of shallower snowpack areas that may be more faceted.

Avalanche Problems

Wind Slabs

New snow, warm temperatures and wind on Tuesday will form dense new wind slabs in high elevation lee terrain. At lower elevations where rain is expected, loose wet avalanches are also possible.
Be cautious as you transition into wind affected terrain.>Stay off recent wind loaded areas until the slope has had a chance to stabilize.>

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

Elevations: Alpine, Treeline.

Likelihood: Likely

Expected Size: 1 - 3

Persistent Slabs

After last week's storm there are questions regarding the reactivity and distribution of buried surface hoar which lies over a metre below the surface in many areas. This uncertainty should be met with conservative terrain selection.
Be aware of the potential for large, deep avalanches due to the presence of buried surface hoar.>Dig down to find and test weak layers before committing to a line.>

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely - Possible

Expected Size: 2 - 4

Cornices

Recent storms have formed very large and unsupported cornices, and at least one person has taken an unexpected ride. Use extra caution around ridge crests in the alpine.
Give cornices a wide berth when travelling on or below ridges.>

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

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 3