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Avalanche Forecast

Archived

Dec 28th, 2023–Dec 29th, 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 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.

Regions

Kitimat, Nass, Rupert, Shames.

Storm slabs are the main problem at upper elevations. Uncertainty remains around the reactivity of some deeply buried weak layers.

Confidence

No Rating

Avalanche Summary

On Wednesday there were reports from the Shames backcountry of two ski cuts that produced small (size 1) avalanches and one large (size 2.5) naturally occurring slab. See this MIN post for more details from that day.

Looking forward to the coming days there will be potential for more natural and human-triggered avalanches with the stormy and warm forecast conditions.

Snowpack Summary

35-50cm of storm snow has accumulated over the last several days, bonding poorly to a slippery rain crust that formed on Christmas. With forecast high freezing levels and rain, the upper snowpack is likely to be wet and/or crusty. At upper elevations, strong winds from variable directions have likely built reactive slabs on many aspects in open areas and near ridge crests.Two buried surface hoar layers can still be found in isolated areas, buried 75-100 cm, and 120-200 cm deep. The remaining mid and lower snowpack contains several well-bonded crusts. Snow depths are highly variable depending on elevation, and decrease rapidly below treeline.

Weather Summary

Thursday Night

Cloudy. Light to moderate rain: 7mm near Terrace, 15mm near Kitimat, expected with snow above 1500 m and freezing levels climbing to 2200 m. 30-50 km/h southerly winds. Treeline temperatures around 1 °C.

Friday

Cloudy. Light rain 3 mm, freezing levels climbing to to 2300 m. 40 km/h southeast wind. Treeline temperatures around 2 °C.

Saturday

Cloudy. Light to moderate rain 5-10 mm, freezing level around 1650 m. Strong southeasterly wind. Treeline temperatures around 2 °C.

Sunday

Cloudy. No precipitation expected, 25-45 km/h southwesterly winds. Freezing level dropping to 500m and a high of -3 °C. at treeline.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • As the storm slab problem gets trickier, the easy solution is to choose more conservative terrain.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.

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.

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.