Avalanche Forecast

Archived

Feb 7th, 2023–Feb 8th, 2023

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

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, West Purcell, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

Continued snowfall and wind have created dangerous avalanche conditions, especially around wind-loaded slopes. Sheltered terrain will likely offer the best and safest riding.

Confidence

Moderate

Avalanche Summary

On Tuesday, explosives control had several deep persistent slab results to size 3.5.

On Monday, A skier accidental avalanche was observed in the Sun Peaks backcountry. The avalanche was a size 2 and is suspected to have run on a weak layer of surface hoar from late January. Several natural storm slab and wind slab avalanches were reported, size 1-2.5, on east and north aspects at treeline and alpine.

On Sunday, several natural slab avalanches were observed in the region, size 1-2.5, on all aspects between 1600 m and 2400 m. A size 2 skier accidental storm slab avalanche was reported at upper treeline. The avalanche was 30 cm deep and fractured on an unsupported roll.

On Saturday, numerous natural storm slab avalanches were reported throughout the region to size 3. Storm slabs were particularly touchy between 1800 m and 2400 m on north and east aspects in lee areas. A skier accidental storm slab avalanche size 2.5 was reported on an east aspect at 2350 m.

Snowpack Summary

Flurries continue to build upon previous storm snow totals bringing 45-60 cm of new snow to the Monashees and 30-75 cm to the Selkirks and west Purcells. Southwesterly winds continue to transport storm snow into deep pockets in lees. This storm 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 crust that extends up to 1800 m in the northern part of the region and up to 2000 m further south. This crust is buried about 40 to 100 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 120 cm deep. These weak layers are still on our radar, although snowpack tests are indicating they may be 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

Tuesday Night

Cloudy with flurries, 5-10 cm accumulation. The eastern and southern Selkirks and west Purcells will see locally higher amounts of 15 cm. Ridge wind west 40 km/h easing to light by morning. Alpine temperatures reach a low of -5 °C. Freezing levels drop to valley bottom.

Wednesday

Cloudy with sunny periods in the afternoon and isolated flurries, 1-5 cm accumulation. Ridge wind west 20 km/h. Alpine temperatures reach a high of -6 °C. Freezing level 1000 metres.

Thursday

Sunny with cloudy periods in the afternoon and isolated flurries, 2-5 cm accumulation. Southwesterly ridge wind 40-60 km/h. Alpine temperatures reach a high of -4 °C. Freezing level 1000 metres.

Friday

Cloudy with flurries, 5-10 cm accumulation. Westerley ridge wind 20-40 km/h. Alpine temperatures reach a high of -3 °C. Freezing level 1200 metres.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

Continue to make conservative terrain choices while the storm snow settles and stabilizes.
Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
Avoid open slopes and convex rolls at and below treeline where weak layers may be preserved.
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.

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.

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.