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Avalanche Forecast

Archived

Apr 19th, 2023–Apr 20th, 2023

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

Regions

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

Riders must manage various avalanche concerns that vary by elevation and aspect. Observe your local conditions and let that inform your terrain choices.

Confidence

Moderate

Avalanche Summary

A number of persistent slab avalanches were reported on Tuesday, up to size 2. They were a combination of explosive and skier triggered, and all appear to have failed on a recently buried (April 1) surface hoar/crust combination. All reported avalanches occurred in the western Purcells.

In the Selkirks the avalanche activity appears to be slowing. However, many natural and human-triggered avalanches were reported last week. Many of these are sliding on recently buried melt-freeze crusts, including a fatal avalanche in the western Purcells and a close call near Revelstoke.

Snowpack Summary

Dry, powder snow remains at higher elevations on north-facing terrain. While multiple melt-freeze crusts or moist snow are likely to be found on steep solar slopes and at lower elevations.

A layer of surface hoar persists down roughly 50 to 100 cm from the surface and appears to be variable in its distribution. The surface hoar may be sitting on top of a thin melt-freeze crust on all but true north-facing slopes. Despite a decrease in avalanche activity on this layer, avalanche professionals continue to closely monitor it.

The mid-snowpack is strong. However, the November depth hoar remains at the base of the snowpack and remains a concern in rocky, shallow, variable depth snowpack areas at treeline and above.

Weather Summary

Wednesday night

Cloudy with clear periods. Light west ridgetop winds. Treeline temperature 0 to -5 C.

Thursday

Cloudy with sunny periods. Light south ridgetop winds. Treeline temperatures 0 to -5 C. Freezing level 1800 m.

Friday

Mix of sun and cloud. Light south ridgetop winds. Treeline temperatures 0 to -5 C. Freezing level 1700 m.

Saturday

Mostly cloudy with scattered flurries. Light south ridgetop winds. Treeline temperatures 0 to -5 C. Freezing level 1700 m.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Closely monitor how the new snow is bonding to the crust.
  • Be alert to conditions that change with elevation and sun exposure.
  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.

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.