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Avalanche Forecast

Archived

Jan 7th, 2020–Jan 8th, 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 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 may remain touchy and could step down to deeper weak layers in parts of the region. Around Coquihalla where deeper weak layers aren't present, the danger may be Considerable. Nonetheless, the snowpack will need time to stabilize with all the recent snowfall.

Confidence

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

Weather Forecast

TUESDAY NIGHT: Cloudy with snowfall, accumulation 5 cm in the north of the region and 15 to 30 cm in the south of the region, moderate southwest wind, alpine temperature -5 C, freezing level 1200 m.

WEDNESDAY: Clear skies in the north of the region and light snowfall in the south of the region, accumulation 2 to 5 cm, light northwest wind, alpine temperature -11 C, freezing level below valley bottom.

THURSDAY: Clear skies, light northwest wind, alpine temperature -11 C, freezing level below valley bottom.

FRIDAY: Cloudy with snowfall, accumulation 5 to 10 cm, moderate to strong southwest wind, alpine temperature -9 C, freezing level below valley bottom.

Avalanche Summary

It is possible that a natural avalanche cycle occurred on Monday during the peak of the storm. Although naturally triggered avalanche activity is expected to decrease into Wednesday, human-triggered avalanches will remain likely to very likely.

Snowpack Summary

Around 20 to 30 cm of snow accumulated in the north of the region and 40 to 60 cm in the south of the region. Below around 1500 m, most of this fell as rain. The snow fell with strong southwest wind, likely forming the deepest and touchiest 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 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 deeper concerns near Coquihalla summit.

Terrain and Travel

  • Travel in alpine terrain is not recommended.
  • 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.
  • If triggered, storm slabs in-motion may step down to deeper layers and result in very large avalanches.

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.