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Avalanche Forecast

Archived

Apr 13th, 2023–Apr 14th, 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 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, 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.

Three different things to consider: at low elevations loose wet avalanches, often running on a crust; lingering dry storm slabs on shady slopes at high elevations; and on southerly aspects at higher elevations is the worst of the bunch -- dry snow sitting on a crust.

Confidence

Low

Avalanche Summary

A serious avalanche incident occurred in the backcountry just east of Revelstoke on Wednesday. Details are available here. This is representative of the recent storm snow above a crust problem.

Otherwise, reports from Monday and Tuesday included many more storm slab and wind slab avalanches, several that were noted for being triggered remotely (from a distance) and a significant number of avalanches attributed to the problematic late-March and early April failure planes discussed in our snowpack summary, now buried under the full depth of recent snowfall. The presence of surface hoar and facets in particular has been noted in some of the more prominent reports of touchy conditions from the past few days.

Looking forward, the need for backcountry travelers to manage a wide range of avalanche concerns that vary by elevation and aspect continues.

Snowpack Summary

Recent storm snow totals at higher elevations (where it is wintery and the snow is dry) are around 30-60 cm, with up to 100 cm reported at high elevations on the west side of the Purcells (e.g. near the Bugaboo group). And of course it's deeper on lee features

All this snow overlies either a widespread melt-freeze crust buried April 7, a weak interface of faceted snow and surface hoar buried at the end of March, or some combination of the two. As the recent snow strengthens, both of these interfaces can serve as weak layers; numerous recent avalanches, some with wide propagation, are attributed to each.

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

Weather Summary

Thursday Night

Mix of cloud and clear periods. Light west or southwest winds. Treeline temperatures around -8 with freezing levels to valley bottom.

Friday

Sunny with cloudy periods. Dry. Light west winds. Treeline high temperatures around 0 C with freezing levels to around 1600 m.

Saturday

Increasing cloud with isolated flurries. Light to moderate south winds increasing over the day and evening. Treeline high temperatures around +2 C with freezing levels to 2000 m.

Sunday

Cloudy with trace to 5 cm of snow. South light winds and moderate gusts. Freezing level near 2000 m and treeline temperatures around zero.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Stay in tune with the physical environment, conditions may change throughout the day.
  • If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.
  • In areas where deep persistent slabs may exist, avoid shallow or variable depth snowpacks and unsupported terrain features.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.