Avalanche Forecast

Archived

Jan 5th, 2024–Jan 6th, 2024

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.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

North Columbia, South Columbia, Jordan, North Selkirk, Shuswap, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, North Okanagan, Whatshan.

Stick to conservative terrain today.

Snowfall will continue to build reactive slabs, and we are uncertain how buried weak layers will react to this new load.

Confidence

Moderate

Avalanche Summary

As storm snow began to accumulate on Thursday, human triggered avalanches were observed to size 1.5.

Operators have been testing the buried weak layers, on Thursday explosive control produced up to size 2 slabs on east facing slopes. The last reported persistent slab avalanche on the buried surface hoar was last Saturday. Triggering becomes more likely as storm snow adds load to the snowpack, most likely in upper treeline and alpine terrain.

Snowpack Summary

By Saturday afternoon, storm totals may reach 50 cm in the Selkirks and around 30 cm elsewhere. This snow accumulates over crusts, surface hoar, and facets. Reports suggest it may be bonding poorly.

A crust formed by the early December rain event is found roughly 60 cm deep, and a layer of surface hoar is found 60 to 100 cm deep. Where it exists, the crust makes it harder to trigger the surface hoar layer, but triggering remains a concern at higher elevations where the crust is less prominent.

The lower snowpack is variable throughout the region, facets found at the ground in shallow snowpack areas.

Weather Summary

Friday Night

Cloudy with 5-10 cm of snow in most areas, and up to 20 cm possible in the Selkirks. Southwest winds 40 km/h. Freezing levels below 1000 m.

Saturday

Cloudy with 5-15 cm of new snow. Southwest winds ease, 20-30 km/h. Freezing levels remain below 1000 m with treeline temperatures around -6 °C.

Sunday

Mostly cloudy with a trace of new snow, winds from the northwest 20 km/h. Freezing levels drop to valley bottom, treeline temperature -8 °C.

Monday

Cloudy with a trace of new snow, westerly winds 20-30 km/h. Freezing levels at valley bottom, treeline temperatures -10 °C.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Storm slab size and sensitivity to triggering will likely increase through the day.
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.

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.