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Avalanche Forecast

Archived

Feb 8th, 2016–Feb 9th, 2016

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

Regions

South Columbia.

Skyrocketing temperatures are expected to weaken surface snow layers, make cornices extra fragile and possibly wake up deeply buried weak layers.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

A strong ridge of high pressure is expected to bring sunny skies above valley cloud. Valley cloud tops should be around 1500 m. A warm southerly flow causes alpine temperatures to rise well above 0, with peak warming and sunshine on Tuesday. Some light precipitation may arrive on Thursday with the passage of a warm front.For more details check out https://avalanche.ca/weather.

Avalanche Summary

A cycle of size 1-3 avalanches was triggered naturally and by skiers and explosives on Saturday in response to new snow and very strong SW winds. A few further storm/wind slabs were reported on Sunday. During this widespread cycle, only a couple of persistent slabs were reported. While the likelihood of triggering a persistent slab has gone down, the consequences remain high. Forecast warming may make the persistent slab easier to trigger again. Cornice fall or a surface avalanche could also trigger a persistent slab.

Snowpack Summary

Warm temperatures and sunshine are expected to weaken and moisten surface snow layers. Strong to extreme SW winds on Saturday created wind slabs and cornices in many areas. In sheltered areas, 15-40 cm recent storm snow is settling, and in some places may still be reactive as a soft slab. A rain crust sits below this in parts of the Monashees. In the far south, a layer of surface hoar is buried about 50-80 cm down. Professionals are still monitoring the early January persistent weak layer, down 80-120 cm. The persistent slab above this has become an infrequent performer. However, in specific locations, it still produces hard, sudden results in snowpack tests, and forecast warming could wake it up again.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.

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.