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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 unlikely, human triggered possible.

Regions

South Columbia.

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 light alpine wind from the southwest in the morning becoming moderate to 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 moderate to 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, a few natural wind slabs were observed in the alpine. A MIN report describes a remotely triggered size 3 avalanche on London Ridge. Click here for more details. A skier also triggered a size 1 storm slab on a south aspect at 2000 m elevation. A few natural and explosive triggered cornice releases were also reported but none of these triggered slabs on the slopes below. On Saturday, natural loose dry avalanches up to size 1.5 were reported as well as a couple skier triggered size 1-2 storm slab avalanches. On Thursday through Friday night, widespread natural and human-triggered storm slab avalanches up to Size 3 were reported throughout the region. On Tuesday, storm slabs overlying a weak layer are expected to remain reactive to human triggering. 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 50-80 cm and includes a sun crust on steep sun-exposed slopes, faceted snow, as well as surface hoar on sheltered open slopes. The mid and lower snowpack are generally well settled and stable in deeper snowpack areas but may be faceted and weaker in shallower areas.

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.

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.