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Avalanche Forecast

Archived

Jan 21st, 2022–Jan 22nd, 2022

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 possible, human triggered probable.
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

South Coast Inland.

Major warming and sun are expected to destabilize the snowpack over the weekend. Wind slabs are expected to remain reactive, cornices will continue to weaken, and deep weak layers may begin to wake up. Wet loose activity should be expected on steep sun exposed slopes.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather. Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Weather Forecast

The region now sits under the warm ridge of high pressure which is expected to persist into early next week bringing very high freezing levels and sun. 

Friday Night: Mainly clear, light NW wind, freezing levels 3000 m with an inversion. 

Saturday: Mainly sunny, light NW wind, freezing levels around 3200 m with an inversion. 

Sunday: A mix of sun and cloud, moderate W wind, freezing levels around 3000 m with an inversion, dropping to around 2000 m by Sunday night. 

Monday: Mainly sunny, light NW wind, freezing levels around 2000 m with an inversion. 

Avalanche Summary

On Thursday, natural size 1 sluffing was observed in the north of the region. On Wednesday, a size 1.5 glide slab was observed at 1400 m in the Coquihalla area as well as several size 1 loose wet avalanches sliding on the crust. In the north of the region, a natural size 1 cornice failure was observed on a NE aspect at 2100 m which did not trigger a slab on the slope below. 

Parts of the region are currently under a Special Public Avalanche Warning (SPAW). Check out this new blog post for additional information. 

Snowpack Summary

At higher elevations, 15-30 cm of recent storm snow has buried the widespread January 16 melt-freeze crust which extends into alpine elevations. There have also been reports of a layer of small surface hoar above this crust in the north of the region on polar aspects at treeline and in the alpine but this does not seem to be widespread. The most recent storm snow has formed reactive wind slabs in exposed high elevation terrain, mainly on north and east aspects. At lower elevations, the upper snowpack is moist or wet from the recent rain event. 

The early December crust/facet layer is now typically down 100-150 cm but may be as shallow as 60 cm and as deep as 200 cm with lots of variability through the region. The layer is most prominent between 1700 and 2100 m. The crust appears to be breaking down in the south of the region but remains a concern in the north. The layer has been dormant recently but is a concern for the period of major warming and sun forecast over the weekend. The most likely place to trigger it would be in thin, rocky snowpack areas where it is shallowest. 

Terrain and Travel

  • Be alert to conditions that change with elevation, aspect and exposure to wind.
  • The likelihood of deep persistent slab avalanches will increase with each day of warm weather.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.

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.