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Avalanche Forecast

Archived

Jan 22nd, 2020–Jan 23rd, 2020

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
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 Coast Inland.

An intense storm will create very dangerous avalanche conditions on Thursday.

Confidence

Moderate - Forecast snowfall amounts are uncertain. Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

WEDNESDAY NIGHT: Frontal system arrives overnight with 10-15 cm of snow above 1700 m, strong wind from the southwest, alpine temperatures rise to -2 C.

THURSDAY: Heavy snowfall in the south of the region (20-40 cm) and moderate to heavy snowfall in the north (15-25 cm), rain below 1500 m, strong wind from the southwest, alpine high temperatures around -1 C.

FRIDAY: Another 5-15 cm of snow, moderate wind from the southwest, alpine high temperatures around -3 C.

SATURDAY: Cloudy with some light flurries, light wind from the southwest, alpine high temperatures around -3 C.

Avalanche Summary

The incoming storm will increase the likelihood of storm slab, deep persistent slab, and wet loose avalanches. In the past few days there have been a few reports of small (size 1) slab avalanches in the northern part of the region and wet loose avalanches around the Coquihalla.

Snowpack Summary

New snow will accumulate above 1500 m creating new storm and wind slabs. The new snow is burying a mix of old wind slabs, crusts, and moist snow.

There are currently no concerns about deep weak layers in the south of the region (e.g. Coquihalla).

There have been two layers of concern in the northern half of the region (e.g. Duffey, Hurley). One is a weak layer of surface hoar buried about 100 cm deep that professionals are tracking at treeline in sheltered areas. The other is weak faceted grains and crusts near the bottom of the snowpack, that is most likely to be triggered in shallow rocky start zones.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow, wind, or rain.
  • Avoid exposure to overhead avalanche terrain, avalanches may run surprisingly far.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

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.