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Avalanche Forecast

Archived

Feb 19th, 2023–Feb 20th, 2023

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

Regions

Vancouver Island, East Island, North Island, South Island, West Island.

The north island is looking like the hotspot on Monday, with lower freezing levels, heavy snowfall and strong northwest winds forming increasingly large and reactive wind slabs throughout the day. Further south and at lower elevations, warmer temperatures and rain mean wet loose avalanches will be the main concern. The underlying crust could make both wet loose and wind slab avalanches more likely.

Confidence

Moderate

Avalanche Summary

On Friday our field team observed evidence of a natural storm slab cycle to size 2. These avalanches were generally on northwest aspects at treeline. They ran on a crust that is now 20-70 cm deep.

Snowpack Summary

Rain at lower elevations will soak the upper snowpack. At higher elevations, 10-25 cm of new snow will accumulate by the end of the day. Northwesterly winds will strip windward slopes and create fresh wind slabs in lee area. A crust can be found down 20-70 cm that extends to mountain tops on all aspects. Recent reports suggest this crust is bonding poorly to the snow above.

The remainder of the snowpack is consolidated and strong.

Weather Summary

Sunday night

Mainly cloudy with wet snowfall or showers. Trace to 8 mm accumulation in most areas except Mount Cain which may receive up to 15 cm of new snow. Freezing levels in the south are 1500-2000 m, and 1100 m in the north. Ridge wind northwest 50 km/h gusting to 90 km/h.

Monday

Periods of wet snow mixed with rain, 10-20 mm of accumulation. Alpine temperatures reach a high of 2 °C. Ridge wind west 45 km/h gusting to 90 km/h. Freezing level up to 2000 m in the south, 1300 m in the north.

Tuesday

Cloudy with snowfall, 5-15 cm accumulation. Alpine temperatures reach a high of -1 °C. Ridge wind north 20 km/h gusting to 75 km/h. Freezing level 1100 metres.

Wednesday

Mainly sunny with cloudy periods and isolated flurries. Alpine temperatures reach a high of -8 °C. Ridge wind northeast 10-30 km/h. Freezing level at valley bottom.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Closely monitor how the new snow is bonding to the crust.
  • The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.