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Avalanche Forecast

Archived

Apr 8th, 2023–Apr 9th, 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 and human triggered avalanches likely.
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.

Regions

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

Southwest winds may have developed wind slabs at higher elevations.

Keep an eye on conditions and be ready to change your plans as Sunday brings a change in the weather.

Confidence

Moderate

Avalanche Summary

Friday saw wind slab and storm slab avalanches. The wind slab avalanches were triggered remotely and with ski cuts. Both were in the alpine, on northerly aspects and were 30 cm deep running on facets that were buried on April 1st. In the northern part of our region, there was a size 2 natural storm slab avalanche. This occurred in the alpine on an east-facing slope and also failed on a surface that was buried 30 cm down.

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 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

By Sunday morning 15 to 20 cm of recent storm snow will be added to the 15 to 40 cm of settling snow. Southerly winds will be increasing and may start creating fresh wind slabs out of this top layer of snow in exposed terrain. A widespread crust is present 30 to 50 cm below the surface, except for on north-facing slopes at treeline and above. In these locations, instead of a crust, you may find faceted surfaces, and surface hoar in sheltered terrain. Further down in the snowpack, 60 cm down, a surface hoar layer has been reactive to human triggering. This has occurred primarily in the Selkirks, on northeasterly slopes from 1700 m to 2100 m.

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

Saturday Night

Mostly cloudy, around 5 cm accumulation, winds southwest 25 km/h, freezing levels 1500 m.

Sunday

Cloudy, 5 to 8 cm accumulation throughout the day, winds south 30 to 40 km/h, freezing levels potentially getting up to 2000 m.

Monday

A mix of sun and cloud, up to 10 cm accumulation by the morning with another 10 to 20 cm during the day, winds southwest 30 km/h switching to the northeast by the end of the day, freezing levels 1500 to 2000 m.

Tuesday

Mostly cloudy, up to 8 cm accumulation in some places, winds southwest 20 to 25 km/h, freezing levels to 1500 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.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • 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

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.

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.