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Avalanche Forecast

Archived

Mar 25th, 2020–Mar 26th, 2020

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

Regions

Northwest Coastal.

New snow and elevated winds will introduce fresh surface instabilities to the region.

Confidence

Low - Forecast snowfall amounts are uncertain. Uncertainty is due to the limited number of field observations.

Weather Forecast

Wednesday night: Becoming cloudy with flurries bringing 5-10 cm of new snow, increasing in the morning. Moderate to strong west winds.

Thursday: Cloudy with continuing snowfall bringing 10-15 cm of new snow, easing overnight. Moderate to strong southwest winds. Alpine high temperatures around -5.

Friday: Cloudy with isolated flurries and up to 5 cm of new snow, increasing overnight. Moderate to strong southwest winds, increasing overnight. Alpine high temperatures around -5.

Saturday: Cloudy with continuing flurries bringing 5-10 cm of new snow, continuing overnight. Moderate to strong southwest wind. Alpine high temperatures around -5.

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

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 to 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.