Avalanche Forecast

Archived

Dec 22nd, 2023–Dec 23rd, 2023

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 unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

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

Northwest Coastal, Boundary, Stewart, Ningunsaw, Ningunsaw, Ningunsaw.

Look for sheltered terrain to avoid wind slabs.

Storm snow likely needs time to bond with the old snow surface.

Confidence

Moderate

Avalanche Summary

Initial reports suggest widespread natural avalanche activity occurred to size 1.5 throughout the storm, with most avalanches from north and west facing slopes due to strong southerly winds.

Explosive control produced the same results, with remotely triggered slab avalanches up to 300 m away indicating touchy conditions.

We expect slabs to continue to be reactive to human triggers.

Snowpack Summary

20-30 cm of recent storm snow has been redistributed by strong winds to deeper deposits on north and east facing slopes. Low elevations may have a surface crust from warm temperatures and rain.

A spotty layer of surface hoar can be found around 25-45 cm deep in sheltered terrain features at and below treeline. The distribution of this layer is not well known.

A layer of facets buried at the end of November can be found 100 to 200 cm below the surface. The snowpack depth varies between 150 and 250 cm at treeline.

Weather Summary

Friday Night

Cloudy with flurries, westerly winds 30-40 km/h. Freezing levels at valley bottom.

Saturday

Mainly cloudy with 3-7 cm of snow, southerly winds 40-60 km/h. Freezing levels rise to 500 m, treeline temperature -5 °C.

Sunday

Mainly cloudy and up to 5 cm of snow. Southerly winds, 60-90 km/h. Freezing levels remain around 500 m. Treeline temperatures near -5 °C.

Monday

Mostly cloudy with possible flurries and southerly winds, 60-80 km/h. Freezing levels rise towards 1000 m, treeline temperatures around -3 °C.

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.
Avoid rock outcroppings, convexities, and anywhere the snowpack is thin and/or variable.
Closely monitor how the new snow is bonding to the old surface.

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.

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.