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Avalanche Forecast

Archived

Mar 24th, 2020–Mar 25th, 2020

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

Regions

Northwest Coastal.

Forecast confidence is low due to a lack of field observations. New and reactive wind slabs are expected to exist on a wide range of aspects in higher elevation terrain.

Confidence

Low - Uncertainty is due to the limited number of field observations.

Weather Forecast

Tuesday night: Clear. Moderate north winds, increasing into the morning.

Wednesday: Sunny, becoming cloudy overnight. Moderate to strong north winds. Alpine high temperatures around -5.

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

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

Avalanche Summary

No new avalanches were observed on Monday from limited reports. 

Recently formed wind slabs may remain reactive to human triggering over the coming days.

Snowpack Summary

Around 10 to 15 cm of snow fell Sunday night in the south of the region with strong, variable winds, likely forming wind slabs in exposed terrain features on all aspects. Wind was the primary driver of new slab formation in the north of the region.

New wind slabs likely sit on a melt-freeze crust on sun-exposed slopes and on previously wind-affected snow elsewhere. Slabs formed over crust may take a bit longer to stabilize.

A layer of surface hoar crystals is buried around 30 to 60 cm in sheltered areas at and below treeline. Recent observations of this layer are limited.

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

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.