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Avalanche Forecast

Archived

Mar 15th, 2022–Mar 16th, 2022

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Coast Inland.

Storm slabs likely remain triggerable by riders at upper elevations on Wednesday. Tune into any signs of instability like cracking or recent avalanches as indicators to back off into lower angle or less wind-loaded terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Convective squalls may produce localized heavy snowfall overnight. Exact amounts and locations are difficult to predict in this kind of pattern. The Coquihalla is a likely candidate.

Tuesday night: Snowfall 5-10 cm, 30-40 km/h southwest wind, alpine temperature -5 C. Freezing level 700m.

Wednesday: Flurries 1-3 cm, 20-30 km/h southwest wind, treeline temperature -5 C. Freezing level 1400 m.

Thursday: Flurries up to 5 cm, 30-40 km/h southwest wind, treeline temperature -4 C. Freezing level 1400 m.

Friday: Flurries bringing a trace, 20-30 km/h southwest wind, treeline temperature -5 C. Freezing level 1400 m.

Avalanche Summary

On Tuesday, debris from a natural size 2 storm slab was observed in a low elevation runout zone in the Coquihalla.

On Monday, natural and skier controlled size 1 storm slabs were observed in wind loaded convexities around treeline.

The last reported persistent slab activity was on Wednesday when a rider triggered a persistent slab avalanche along the Duffey at 2000 m on a northeast aspect. Another suspected persistent slab avalanche was triggered by a rider on Tuesday in the north of the region. Both slabs were around 30 to 40 cm thick, resulting in small avalanches (size 1 to 1.5). This problem appears to be spotty and isolated but remains possible for humans to trigger, where it exists.

Snowpack Summary

10-20 cm of recent snow has been redistributed into wind slabs at upper elevations. The recent snow sits over variable surfaces including a hard melt-freeze crust on solar aspects and low elevations and perhaps a thin layer of surface hoar or faceted snow in sheltered areas.

Around 30 to 60 cm deep, sugary faceted grains may be found around a melt-freeze crust that formed February in the north of the region (e.g., Duffey, Hurley). The layer has been most problematic on isolated north to northeast aspects around 1900 to 2100 m. Check out this forecaster blog for more info.

Various crusts may be found in the south of the region (e.g., Coquihalla, Manning) but reports suggest they are bonding to the snowpack and are not an avalanche concern.

There are no deeper concerns at this time.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Be aware of the potential for large avalanches due to the presence of buried persistent weak layers.

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.