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Avalanche Forecast

Archived

Mar 16th, 2023–Mar 17th, 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.

Assess for wind slabs in steep terrain and use caution on southerly slopes if the sun is out.

Confidence

Moderate

Avalanche Summary

A handful of wind slab and storm 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 20 cm of recent storm snow in alpine terrain near ridge tops.

Looking forward, we expect that riders could continue to trigger wind slabs in lee terrain features at higher elevations. Periods of sun and mild weather will increase the likelihood of loose wet avalanches on sun-exposed slopes and cornice falls.

Snowpack Summary

Around 15 to 25 cm of recent snow overlies large (10 mm) surface hoar crystals in terrain sheltered from the wind, wind-affected snow in wind exposed terrain, and a hard melt-freeze crust on sun-exposed slopes. The wind has been blowing from the southwest, meaning that the deepest and touchiest deposits are likely found in north to east lee terrain features near ridges. Relatively mild 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 is currently dormant but it may become active with any rapid change to the snowpack, such as rapid loading (e.g., 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

Thursday Night

Partly cloudy with no precipitation, 20 km/h south wind, treeline temperature -6 °C.

Friday

Partly cloudy with no precipitation, 20 km/h south wind, treeline temperature -5 °C, freezing level 1100 m.

Saturday

Mostly clear skies with no precipitation, 30 km/h southeast wind, treeline temperature -4 °C, freezing level 1200 m.

Sunday

Cloudy with light snowfall, accumulation 1 to 3 cm, 20 to 30 km/h southeast wind, treeline temperature -4 °C, freezing level 1200 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Carefully evaluate steep lines for wind slabs.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
  • Conditions may have improved, but be mindful that deep instabilities are still present.

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.

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.

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.