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Avalanche Forecast

Archived

Feb 17th, 2020–Feb 18th, 2020

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

Regions

Sea To Sky.

Sun and warm temperatures have helped the snowpack settle and bond. Keep an eye on sunny slopes warming through the day, move to more shaded terrain and avoid overhead hazards if the surface snow becomes moist or wet.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

MONDAY NIGHT: Partly cloudy. Alpine low temperature -8 C. Northwest wind 10-15 km/hr. Freezing level valley bottom.

TUESDAY: Sunny. Alpine high temperature -3 C. Northeast wind 10-20 km/hr. Freezing level 1000 m.

WEDNESDAY: Sunny with clouds. Alpine high temperature +2 C. South wind 15-20 km/hr. Freezing level 1500 m.

THURSDAY: Mix of sun and cloud. Alpine high temperature -1 C. Southwest wind 10-20 km/hr. Freezing level 1200 m.

Avalanche Summary

Skiers triggered loose, dry sluffing in steep terrain on Sunday. On Saturday, small size (1-1.5) wind slab avalanches were triggered by skiers and explosives in the alpine and treeline. On Friday fast moving storm slabs with crowns averaging 20 cm in depth were quite sensitive to human triggers and explosive control work to size 1.5. Control work also produced cornice failures to size 2.5.

A very large (size 3.5) avalanche was observed on February 9th near Whistler on a steep north face at 2400 m. It is suspected to have failed on a layer of facets on a crust from late November. This very large event demonstrates the ongoing need for caution in aggressive alpine terrain.

Snowpack Summary

10-30 cm recent snow has be redistributed by southwesterly winds and a crust has formed on solar aspects. The new snow overlies wind affected snow in the alpine, a crust on solar aspects, and lower density snow or spotty surface hoar in sheltered terrain. 

A rain crust sits 30-50 cm below the surface at elevations below 2000 m. The bond at this interface appears to be reasonably strong and the mid pack well settled. 

While weak faceted grains and crusts near the base of the snowpack have mostly not been a problem recently, a very large avalanche was observed on this layer on Feb 9. The problem appears isolated to very aggressive alpine terrain and is likely more prevalent in inland parts of the region.

Terrain and Travel

  • Be alert to conditions that change with elevation and wind exposure.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet

Problems

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.

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.