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Avalanche Forecast

Archived

Jan 8th, 2020–Jan 9th, 2020

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.

Storm slabs might remain sensitive to human triggering and could step down to deeper weak layers in parts of the region. There is uncertainty how fast the snowpack will gain strength after the recent snow storm.

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength.

Weather Forecast

WEDNESDAY NIGHT: Cloudy with clear periods and isolated flurries, light northwest wind, alpine temperature -15 C, freezing level below valley bottom.

THURSDAY: Cloudy with sunny periods, moderate northwest wind, alpine temperature -11 C, freezing level at valley bottom.

FRIDAY: Cloudy with snowfall, accumulation 10 to 15 cm, moderate to strong southwest wind, alpine temperature -7 C, freezing level around 600 m.

SATURDAY: Cloudy with flurries, up to 5 cm accumulation, light westerly wind, alpine temperature -15 C, freezing level around 700 m.

Avalanche Summary

On Tuesday, several natural and skier triggered slab avalanches of size 1 were observed. One wet loose avalanche of size 2.5 was reported. It is possible that a natural avalanche cycle occurred on Monday during the peak of the storm. 

Snowpack Summary

Around 30 to 40 cm of snow accumulated in the north of the region and 40 to 60 cm in the south of the region in the last few days. Below around 1500 m, most of this fell as rain. The snow fell with strong southwest wind, likely forming the deepest and most sensitive slabs in lee terrain features. 

Deeper in the snowpack:

  • The snow loaded a touchy weak layer of feathery surface hoar in sheltered areas above 1800 m. Areas such as Manning, Henning, Stoyoma, Duffey, and Hurley should be treated as suspect.
  • A persistent weak layer is present near the bottom of the snowpack in the northern half of the region (e.g., Duffey, Hurley). The weak layer of sugary faceted grains exists around a hard melt-freeze crust from mid-November. This is an indicative snowpack setup for large and destructive avalanches. The likelihood of human-triggered avalanches decreases as the layer gets deeper but the consequence of triggering it would be severe.
  • There are currently no concerns deeper in the snowpack near Coquihalla summit.

Terrain and Travel

  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
  • Don't let the desire for deep powder pull you into high consequence terrain.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.

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.

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.