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Avalanche Forecast

Archived

Feb 7th, 2016–Feb 8th, 2016

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 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.

Regions

South Columbia.

Skyrocketing temperatures make avalanche forecasters nervous. Deeply buried weak layers could wake up, creating very large avalanches.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain on Monday

Weather Forecast

Bring out the flip flops! A strong ridge of high pressure is expected to bring mainly sunny skies (above valley cloud) with no precipitation for the next three days. A warm southerly flow causes the freezing level to rise as high as 3000 m by Tuesday. Alpine temperatures should be well above 0.For more details check out https://avalanche.ca/weather.

Avalanche Summary

A widespread cycle of size 1-2 avalanches was triggered naturally and by skiers and explosives on Saturday in response to new snow and very strong SW winds. During this cycle, only one persistent slab was reported. It was triggered by explosives near Revelstoke and failed on the early January layer. 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.

Snowpack Summary

Strong to extreme SW winds on Saturday created wind slabs and cornices in many areas. Wind slabs may be lingering lower in start zones than normal due to the high wind speed. 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. During Saturday's avalanche cycle, there was only one reported persistent slab, triggered with explosives. Prior to that, more than a week has passed since the last report of a persistent slab. However, in specific locations, it still produces hard, sudden results in snowpack tests, and forecast warming could wake it up again.

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.

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.