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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

North Columbia.

Additional snow and moderate winds on Thursday may activate recently formed storm slabs at treeline and above. Consider the hazard to be one-step higher if localized areas receive more than 15 cm of snow during the day on Thursday.

Confidence

Moderate - Timing of incoming weather systems is uncertain

Weather Forecast

WEDNESDAY NIGHT: Partly cloudy / Light, southwesterly winds / Alpine low -3 C / Freezing level 1500 m.

THURSDAY: Showers and alpine flurries; 5-10 mm. / Moderate, southwesterly winds / Alpine high 2 C / Freezing level 2200 m.

FRIDAY: Rain (snow above roughly 1700 m); 15-25 mm. / Strong, southwesterly winds / Alpine high -1 C / Freezing level 1900 m.

SATURDAY: Mix of sun and cloud / Light, northwesterly winds / Alpine high 0 C / Freezing level 1900 m.

Avalanche Summary

On Tuesday, a natural size 2.5 peristent slab avalanche was reported on a west aspect at 2750 m. Additionally, a skier triggered size 2 storm slab avalanche was reported on an east aspect at 2700 m.

On Monday, a skier remotely triggered a size 2 storm slab from 10 m away on a steep north-facing feature in the alpine; the crown was 20-30 cm deep. A size 2 natural avalanche was observed on a steep east aspect at 2200; the crown was 50 cm deep.

On Sunday, two size 2 storm slab avalanches were triggered by skiers on east aspects at 2200 m. A group of backcountry skiers remote triggered a size 2 storm slab avalanche from 50 m away, failing on a southeast slope at 2250 m. One natural size 2 storm slab avalanche was observed on a steep, north aspect also around 2200-2300 m.

Snowpack Summary

Sun and rising freezing levels are settling the 20-40 cm recent snow on all slopes to 2000 m and sunny slopes in the alpine. Where dry snow remains, pockets of reactive storm snow have developed 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.