Avalanche Forecast

Archived

Dec 22nd, 2023–Dec 23rd, 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 unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Kitimat, Nass, Rupert, Seven Sisters, Shames, Howson.

Buried surface hoar layers are adjusting to the significant storm totals.

Minimize your exposure to convex rolls and large open slopes, especially at treeline elevations.

Confidence

Moderate

Avalanche Summary

We expect widespread natural activity to have occurred on Friday as the wind and snow continued. On Thursday numerous size 2 wind slabs were reported, naturally and human triggered.

Several slab avalanches up to size 2 have been reported this week on the buried surface hoar layers, primarily on north facing slopes around treeline. These reports include natural and remote human triggers.

Snowpack Summary

Up to 65 cm of recent storm snow has been redistributed by strong winds to deeper deposits on north and east facing slopes. Low elevations received mostly rain, and likely hold a surface crust.

Two buried layers of surface hoar are widespread in the mid snowpack, buried 45-80 cm, and 90-130 cm deep.

The remaining mid and lower snowpack contains several crusts from early in the season that are generally well-bonded to the surrounding snowpack. Snow depths are highly variable depending on elevation, and decrease rapidly below treeline.

Weather Summary

Friday Night

Cloudy with possible flurries, westerly winds 40-50 km/h. Freezing level 500 m.

Saturday

Cloudy with 1-3 cm of snow, southerly winds increase over the day, from 40 to 60 km/h. Freezing levels around 700 m, treeline temperature -5 °C.

Sunday

Cloudy with snow starting midday, 5-10 cm. Freezing levels between 500-1000 m, and treeline temperatures around -2 °C. Southerly winds strengthen to above 100 km/h.

Monday

Mostly cloudy with flurries. Freezing levels rise towards 1500 m, treeline temperatures approach 0°C. Southerly winds 60-100 km/h.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Don't be too cavalier with decision making, storm slabs may remain sensitive to human triggering.
Storm slabs in motion may step down to deeper layers resulting in large avalanches.
Be especially cautious as you transition into wind affected terrain.
Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

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.