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Avalanche Forecast

Archived

Jan 24th, 2015–Jan 25th, 2015

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

Regions

Sea To Sky.

The snowpack has been rain-soaked at most elevations, while new wind slabs exist at ridge top. Pay close attention to conditions that change with elevation.

Confidence

Fair - Due to the number of field observations

Weather Forecast

A mix of sun and cloud is forecast for Sunday and Monday as a weak ridge pushes a pacific moisture stream to the north of the region. On Tuesday the region is forecast to receive up to 15cm of snow. Ridgetop winds are forecast to remain strong and southwesterly on Sunday and Monday, and then drop to moderate values on Tuesday. Freezing levels are expected to hover around 3000m on Sunday and Monday, and then drop to about 1500m on Tuesday.

Avalanche Summary

At the time of publishing this bulletin, observations were extremely limited. That said, I'm sure recent rain sparked a round of loose wet avalanche activity, while wind slabs may have been triggered at higher elevations. Although unlikely, deep persistent avalanches are still a concern as long as the snowpack is wet or moist. Any activity on these deeper weaknesses would be very destructive in nature.

Snowpack Summary

Up to 50 cm of settled storm snow has now been saturated by rain up to about 2100m. At the highest elevations, moist snowfall throughout Saturday was shifted into wind slabs in lee terrain. New cornice development has also been noted. The older storm snow overlies a hard crust and/or surface hoar layer which formed in January. The bond at this interface will be largely elevation dependant, as rain may have penetrated the snowpack enough to dissolve the crust in many areas.Deeper snowpack weaknesses have become unreactive, but a recent snow profile highlights the stark hardness contrast between a deep persistent weakness and the surrounding snow. Scenarios like this with deeply buried soft snow surrounded by hard snow aren't confidence inspiring because it all hinges on the strength of the overlying slab, which is often volatile and susceptible to significant warming and loading. Especially with very heavy triggers (like a cornice fall) in the wrong spot (like a thin snowpack area).

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.