Avalanche Forecast

Archived

Feb 2nd, 2023–Feb 3rd, 2023

Alpine

Natural and human triggered avalanches likely.

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 possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

North Columbia, South Columbia, Esplanade, Jordan, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

630am update:

Avalanche conditions may become increasingly touchy today as strong winds and warming temperatures turn recent snow into reactive storm slabs. In combination with a complex underlying snowpack, this means potential for large, destructive avalanches.

Confidence

Moderate

Avalanche Summary

On Wednesday, most reports came in as dry loose avalanches and sluffing up to size 1. Some areas in the Monashees did see more reactivity in the recent storm snow up to size 1.5. These were easily rider triggered and failed naturally. I suspect avalanche activity will increase on Friday with steady moderate to strong winds and slightly warmer temperatures.

On Tuesday, several rider-triggered storm slab and wind slab avalanches were seen up to size 1, and numerous loose dry avalanches size 1-2 were reported from steeper terrain features.

Last weekend, various deep persistent slab avalanches were also triggered naturally, being large to very large (size 2 to 4). The avalanches occurred on all aspects between 2400 and 2800 m.

High-consequence avalanche activity is ongoing for several weeks now. Most of the avalanches over the past week were released between 1800 and 2800 m, on all aspects.

Your best defence is to stay diligent in choosing low-consequence terrain away from overhead exposure.

See more on the potential of triggering deeper weak layers Forecasters' Blog.

Snowpack Summary

20-50 cm of recent storm snow accompanied by moderate westerly wind will build reactive storm slabs and wind slabs in lee terrain features. The new snow sits above a plethora of old snow surfaces including previously wind-affected snow at upper elevations, a sun crust on steep solar aspects, faceted snow, and surface hoar crystals in wind-sheltered terrain.

Below the recent snow is a melt-freeze near 1800 m which exists in the northern part of the region and up to 2000 m further south. This is buried about 30 to 60 cm deep and may host small facets on the crust.

Deeper in the snowpack two layers of surface hoar which formed in early January are 60 to 100 cm deep. These weak layers continue to be suspect and on the radar, although snowpack tests are starting to indicate they may be slowly strengthening.

Large and weak facets from November are near the base of the snowpack, which continue to produce very large avalanches in the region, as described in the Avalanche Summary.

Weather Summary

Thursday Night

Cloudy with isolated flurries 5 cm. Ridgetop wind 35 - 45 km/h from the southwest. Treeline temperature -6 °C.

Friday

Cloudy with possible sunny breaks and light snow accumulation 5 to 10 cm. Ridgetop wind 20 - 60 km/h from the southwest and treeline temperature rising to -4 °C. Freezing level 1300 m.

Saturday

Cloudy with new snow up to 10 cm. Ridgetop wind 30-50 km/h from the southwest and treeline temperature -5 °C. Freezing level 1400 m.

Sunday

Possible sunny periods and isolated flurries 5 to 10 cm. Ridgetop wind 20 to 45 km/hr from the southwest. treeline temperature -5 °C. Freezing level 1400 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Avoid all avalanche terrain during periods of strong wind.
Storm slab size and sensitivity to triggering will likely increase through the day.
Remain vigilant for changing conditions.
Be aware of the potential for larger than expected storm slabs due to the presence of buried surface hoar.
Be mindful that deep instabilities are still present and have produced recent large avalanches.
Be carefull with sluffing in steep terrain, especially above cliffs and terrain traps.

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.

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.