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Avalanche Forecast

Archived

Apr 7th, 2023–Apr 8th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

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

6am update: Overnight snowfall amounts were greatest in the Monashees south of Highway 1. If you are seeing more than 20 cm of new snow in your local area, treat avalanche danger as CONSIDERABLE in the alpine.

Confidence

Moderate

Avalanche Summary

On Thursday, there were reports of several cornice triggered avalanches throughout the Monashees up to size 3. These avalanches did not step down to deeper weak layers.

On Wednesday, storm snow continued to be reactive to natural and human triggers. A few surprise skier triggered storm slab avalanches were reported up to size 2. Naturally triggered storm slab and wind slab avalanches were observed up to size 2.5. Many of these avalanches are reported to be failing on a surface hoar layer buried near the end of March or a crust on solar aspects. Avalanche activity has primarily been observed on north and east aspects from 1700 m to 2200 m. Reports indicate that the Selkirks seem to be the most reactive with rider remote-triggered slabs in the upper 50 cm of snow.

Snowpack Summary

10-15 cm of recent storm snow overlies 15-40 cm of settling snow. A widespread crust is found down 20-50 cm, except for on north-facing slopes at treeline and above, where it sits on old, faceted surfaces, and surface hoar in sheltered terrain. A surface hoar layer (down 60 cm) has recently been reactive to human triggering primarily in the Selkirks, especially on northeasterly slopes from 1700 m to 2100 m.

Strong southwest wind will build fresh wind slabs on leeward slopes and behind terrain features.

The mid-snowpack is generally strong but the lower snowpack is a different story. The November facets are still prominent at the base of the snowpack. This layer remains a concern in rocky, shallow, or thin to thick snowpack areas at treeline and above.

Weather Summary

Friday Night

Cloudy with flurries. 5 cm of new snow are expected for most areas of the region, with up to 15 cm in local areas around Revelstoke. Ridgetop wind 40 km/h from the southwest. Freezing levels remain at 1500 m.

Saturday

Mainly cloudy with isolated flurries, 1-3 cm accumulation. Ridgetop wind 30 km/h gusting to 50 km/h from the southwest. Freezing levels 1700 m.

Sunday

Mainly cloudy with isolated flurries, 3-5 cm accumulation. Ridgetop wind 70 km/h from the southwest. Freezing levels fluctuate between 1700 m and 2000 m.

Flurries continue through the night bringing 7-12 cm of new snow.

Monday

Cloudy with flurries bringing mixed precipitation, 15-30 mm expected. Ridgetop wind 50 km/h gusting to 80 km/h from the southwest. Freezing levels fluctuate between 1500 m and 2000 m.

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.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Seek out sheltered terrain where new snow hasn't been wind-affected.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

Problems

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.

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.

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.