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Avalanche Forecast

Archived

Jan 12th, 2020–Jan 13th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

South Coast Inland.

Fluffy unconsolidated snow will hide previously formed wind slabs. Deeper weak layers might still be reactive to human triggers, particularly in the north of the region.

Confidence

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

Weather Forecast

SUNDAY NIGHT: Cloudy with clear periods, moderate northerly wind, alpine temperature -25 C, freezing level below valley bottom.

MONDAY: Mostly sunny, light to moderate northwest wind, alpine temperature -25 C, freezing level below valley bottom.

TUESDAY: Mix of sun and cloud with isolated flurries, moderate west wind, alpine temperature -25 C, freezing level below valley bottom.

WEDNESDAY: Mostly sunny, moderate west wind, alpine temperature -25 C, freezing level below valley bottom.

Avalanche Summary

On Saturday, the snowpack was reactive to explosive triggers. Some avalanches stepped down to a feathery surface hoar layer buried 50-60 cm deep. 

No new avalanches were reported on Friday.

On Thursday, a few explosive triggered storm slab avalanches up to size 2 were reported. One explosive triggered avalanche released on the mid November facet/crust layer.

Snowpack Summary

Unconsolidated fluffy snow of the recent storm sits on a snow surface that was wind affected by moderate to strong southerly wind. The wind formed slabs in lee terrain features in the alpine and around treeline. 

Deeper in the snowpack:

  • The previous storm 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

  • Recent new snow may be hiding windslabs that were easily visible before the snow fell.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.
  • Watch your sluff: it may run faster and further than you expect.

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.