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Avalanche Forecast

Archived

Mar 17th, 2023–Mar 18th, 2023

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 Inland, Kispiox, Microwave-Sinclair, Ningunsaw, Ningunsaw, South Bulkley, South Bulkley, Telkwa.

Watch for reactive slabs in wind loaded terrain. A layer of buried surface hoar is increasing reactivity and propagation.

Monitor snow conditions on sun baked slopes, wet avalanches become more likely in the afternoon as daytime temperatures rise and sun effect increases.

Confidence

Moderate

Avalanche Summary

Slab avalanches were reported over the past few days, being triggered naturally, by riders, and by large loads like cornice falls and vehicles. The avalanches were small to large (size 1.5 to 2.5) and releasing within the 25 cm of recent storm snow in terrain at higher elevations, mostly around ridgelines. Most avalanches were thought to occur on the buried surface hoar layer.

Natural and rider triggered loose wet avalanches were also observed to size 1 from rising temperatures and sunshine.

Snowpack Summary

Around 15 to 25 cm of recent snow overlies large surface hoar crystals in terrain sheltered from the wind and sun, wind-affected snow in wind exposed terrain, and a hard melt-freeze crust on sun-affected slopes.

Southwest winds have created deeper and more reactive deposits on north to east facing terrain features near ridges. Warmer weather and sunny skies may moisten the snow surface on sun-exposed slopes and at low elevations.

The middle of the snowpack is strong and contains numerous hard crusts.

The lower snowpack is composed of weak basal facets. The layer has not produced recent avalanche activity, however it may become active again with any rapid change to the snowpack, such as rapid loading (heavy snowfall or rain) or prolonged and extensive warming. Avoiding thin and rocky slopes is still recommended. Cornices are also very large and a cornice failure could trigger this basal layer.

Weather Summary

Friday Night

Mostly clear skies as freezing levels drop to valley bottom. Moderate southerly winds.

Saturday

Sunny with moderate southerly winds. Freezing levels rise to 1500 m. Alpine high temperature -3 °C.

Sunday

Mostly cloudy with up to 2 cm of snow. Moderate to strong southeast winds. Freezing levels rise to 1000 m.

Monday

Light snowfall continues with cloudy skies and moderate southeasterly winds Freezing levels around 1000 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.