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Avalanche Forecast

Archived

Feb 13th, 2017–Feb 14th, 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 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 possible, human triggered probable.

Regions

Cariboos.

Extra caution is required on Tuesday as freezing levels climb to mountain top elevation and the snowpack sees major warming for the first time this winter. Avoid steep sun exposed slopes during the heat of the afternoon.

Confidence

Moderate -

Weather Forecast

On Tuesday, sunny conditions are expected with moderate alpine wind from the southwest in the morning becoming strong in the afternoon. Freezing levels are forecast to reach around 2800 m with a temperature inversion keeping the valleys colder than the alpine. A layer of valley fog may also develop. On Wednesday, mostly cloudy conditions are expected with light rain beginning in the afternoon. Alpine wind is forecast to be strong from the southwest and freezing levels are expected to remain at around 2500 m. Light rain is forecast to continue Wednesday night and Thursday. 5-10 mm of precipitation is currently forecast between Wednesday afternoon and Thursday evening. Freezing levels are forecast to drop to around 2000 m on Thursday.

Avalanche Summary

On Sunday, four solar triggered size 2 storm slab avalanches were observed on southeast and south aspects at 1400-2200 m. Ski cutting produced two size 1 storm slab avalanches on southeast aspect at 1850 m. Over the weekend, several rider triggered avalanches were reported on the MIN including a size 3 that resulted in a full burial. Click here more details (1). (2), and (3). On Saturday, a natural size 2 storm slab was observed and a size 2 storm slab avalanche was remotely triggered from 60 m away.On Tuesday, storm slabs overlying a weak layer are expected to remain reactive to human triggering. Persistent slab avalanches are possible and smaller avalanches may step down. Extra caution is recommended during the heat of the afternoon, especially on sun exposed slopes. This will become increasingly important through the week as freezing levels remain very high. We have entered the first period of substantial warming following months of sustained cold conditions. Any weaknesses lingering in the snowpack will be tested in the coming days.

Snowpack Summary

The storm snow from Thursday and Friday is settling quickly due to the recent mild temperatures. The snow surface is expected to have undergoing some melting on Monday afternoon on sun exposed slopes. Recent strong winds from the south and west had redistributed the recent storm snow in exposed terrain forming touchy wind slabs. The early February weak layer is typically down 40-70 cm and includes old hard wind slabs and crusts as well as faceted snow and surface hoar on sheltered open slopes. The persistent weakness buried mid-January is now down around 80-100 cm and the surface hoar/facet weakness buried mid-December is down 100-150 cm. These deep persistent weaknesses have the potential to wake up and become reactive with the warmer temperatures.

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.

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.