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Avalanche Forecast

Archived

Feb 13th, 2018–Feb 14th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

Stay disciplined while avalanche danger is heightened. Wind slabs remain reactive to human triggering and forecast new snow is not expected to bond well to the weak surfaces that developed during the clear period.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Tuesday night: Flurries bringing around 6-12 cm of new snow. Light to moderate southwest winds. Wednesday: Mainly sunny. Light to moderate northeast winds. Freezing level to 1000 metres with alpine high temperatures around -7.Thursday: A mix of sun and cloud with increasing cloud and light flurries over the day. Light southwest winds. Freezing levels down to 500 metres with alpine high temperatures of - 11.Friday: A mix of sun and cloud. Light northwest winds. Freezing level to 800 metres with alpine high temperatures around -7.

Avalanche Summary

We have a preliminary report of a snowmobiler that was fatally involved in a cornice failure in the Callaghan area on Saturday. Our understanding is that the individual was parked on or near the cornice when it failed beneath them. This failure resulted in a long fall from ridgetop and the partial burial of the individual in the debris.Reports from Sunday included one observation of a recent natural size 2 cornice release in the Spearhead Range as well as one explosives-triggered size 2 cornice. Warm temperatures and solar exposure caused one natural size 2 loose wet avalanche on a steep alpine slope in the Whistler area.On Saturday, two skier-triggered wind slabs were reported: a size 1.5 wind slab from a cross-loaded feature on a northwest aspect at 1900 m, and a size 2 on a north aspect at 2350 m, both near Whistler. Please see this MIN report for details.On Friday, evidence of a natural cycle which likely occurred near the end of the warming period earlier in the week was reported, with storm slab activity up to size 3 observed on north to east aspects in the Mt Currie area.

Snowpack Summary

Increasing flurries are expected to bring about 15 cm of new snow to the region by Wednesday morning. Beneath the new snow, highly variable snow surfaces exist. From scoured crusty surfaces on south-facing alpine slopes to reactive wind slabs on lee slopes facing roughly north. More recent northerly winds have expanded wind slab formation to a range of other aspects and melt-freeze crust exists up to about 1900 m.On average, 180 cm of settled snow now sits on the mid-January crust which generally shows signs of bonding to the overlying snow; however, it has the potential to wake up with a large trigger such as a cornice fall. Below this, the snowpack is thought to be generally strong and well-settled.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.