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Avalanche Forecast

Archived

Apr 17th, 2019–Apr 18th, 2019

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

Regions

South Columbia.

Additional snow, wind, and warm temperatures on Thursday may activate recently formed storm slabs at treeline and above.

Confidence

Moderate - Timing of incoming weather systems is uncertain

Weather Forecast

WEDNESDAY NIGHT: Partly cloudy / Light, westerly winds / Alpine low 0 C / Freezing level 2000 m.

THURSDAY: Showers and alpine flurries; 5-10 mm. / Moderate, southwesterly winds / Alpine high 4 C / Freezing level 2500 m.

FRIDAY: Rain (snow above roughly 2000 m); 15-25 mm. / Strong, southwesterly winds / Alpine high 2 C / Freezing level 2200 m.

SATURDAY: Mix of sun and cloud / Light, northwesterly winds / Alpine high 1 C / Freezing level 2000 m.

Avalanche Summary

On Tuesday, two naturally triggered size 1.5 storm slab avalanches 25 cm deep were reported on northwest aspects 2200-2400 m.

On Sunday, a skier triggered a size 1.5 wind slab avalanche on a steep convex roll at 2150 m and explosives triggered a size 2 storm slab avalanche at 2350, both avalanches occurred on a northeast aspect.

A natural avalanche Sunday was observed north aspect at 2300 m. The size 2 storm slab avalanche failed on surface hoar around 40-50 cm deep likely buried early April. This isolated layer may see increased stress as temperatures penetrate the snowpack.

Snowpack Summary

Sun and rising freezing levels are settling the 20-40 cm recent snow on all slopes to 2100 m and sunny slopes in the alpine. Where dry snow remains, pockets of reactive storm snow may be found around ridges and lee features. A total of 50-65 cm snowfall through April now overlies a melt-freeze crust and, in select areas, facets or surface hoar. Below treeline snow is disappearing rapidly.

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.