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Avalanche Forecast

Archived

Mar 7th, 2017–Mar 8th, 2017

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

Regions

South Coast.

Heavy storm loading on Tuesday and a deeply buried weak layer are creating tricky conditions. Watch for fresh storm slabs on Wednesday and use extra caution on south facing slopes when the sun is out. Conservative terrain selection remains critical.

Confidence

Moderate -

Weather Forecast

Another 5-10 cm of snow is expected Tuesday overnight with moderate to strong alpine wind from the southwest. A mix of sun and cloud is expected on Wednesday with the potential for isolated snow flurries. Alpine wind is forecast to be moderate from the southwest and freezing levels are expected to reach around 600 m in the afternoon. Similar conditions are expected for Thursday with a mix of sun and cloud, isolated snow flurries, moderate alpine wind from the southwest, and afternoon freezing levels around 800 m. A storm system is currently forecast to arrive Thursday evening and bring 40-50 cm of new snow by midday Friday. Alpine wind should be strong from the southwest during the storm and freezing levels are forecast to reach around 1400 m.

Avalanche Summary

On Monday, a report includes whumphing and a ski cut triggering a size 2 slab which released on the crust layer. Explosives also triggered numerous storm slabs 20-30 cm thick and one stepped down to the crust layer down 40-60 cm. MIN posts from Sunday include whumphing and small skier triggered avalanches on test slopes. On Saturday, a person was fully buried in the Tony Baker Gully near Cypress Mountain. North Shore SAR removed the person from the scene with serious injuries. Click here for more details. On Wednesday, storm slabs are expected to be touchy after the region saw heavy snowfall on Tuesday. Slabs will be particularly reactive in wind loaded terrain. Large persistent slab avalanches remain a serious concern with the snow from the past week releasing on the February weak layers. It may still be possible for a person to directly trigger a persistent slab or a storm slab avalanche could step down.

Snowpack Summary

Another 30-70 cm of snow fell in the North Shore mountains on Tuesday bringing the typical storm accumulation in the past week to 100-200 cm. Recent winds have been from a variety of directions and wind slabs should be expected on all aspects. The recent snow overlies the late-February interface that is composed of a sun crust on southerly aspects and surface hoar on shaded aspects. The recent snow appears to be bonding poorly to this layer and with the cold conditions, the weakness is expected to persist longer than normal for the region. Below this interface is the thick mid-February crust/facet layer which woke up during the natural avalanche cycle on Friday but now appears to be dormant. Below this crust, the mid and lower snowpack appear to be well settled and strong.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.