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Avalanche Forecast

Archived

Mar 26th, 2020–Mar 27th, 2020

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

Regions

Northwest Coastal.

Avalanche hazard will increase as new snow and elevated winds develop a surface instability around the region.

Confidence

Low - Uncertainty is due to the limited number of field observations. Forecast precipitation (either snow or rain) amounts are uncertain.

Weather Forecast

Thursday night: Cloudy with scattered flurries, up to 10 cm. Alpine low temperature -3 C. Moderate southwest wind.

Friday: Cloudy with scattered flurries, 5-10 cm. Alpine high temperature -4 C. Moderate to strong west wind.

Saturday: Flurries and snow, 10-20 cm. Alpine high temperature -5 C. Light to moderate southwest wind.

Sunday: Flurries and snow, 10-20 cm. Alpine high temperature -4 C. Light southeast wind with strong gusts.

Avalanche Summary

A recent large (size 2.5) natural glide slab release was observed on Tuesday. The debris from the release overran the John Little Falls hiking trail. 

Natural glide slab activity has been a regular occurence during recent periods of daytime warming, reinforcing the importance of avoiding glide cracks and areas exposed glide slab hazards.

Snowpack Summary

Flurries will be quickly impacted by increasing winds, redistributing loose snow and building slabs. Surface conditions over the region are likely a mix of recent wind slabs and wind-affected snow as well as melt freeze crust on south aspects and below about 1100 metres.

A layer of surface hoar crystals is buried around 30-60 cm in sheltered areas at and below treeline, shallow enough for human triggering on steep slopes where it is preserved. Recent observations of this layer are lacking.

An early-season layer of faceted grains and a melt-freeze crust can likely be found near the base of the snowpack at high elevations. A large load, such as a large cornice fall, may have potential to trigger it.

Terrain and Travel

  • Storm slab size and sensitivity to triggering will likely increase through the day.

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.