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Avalanche Forecast

Archived

Apr 5th, 2023–Apr 6th, 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, Blue River, Clearwater, Clemina, Esplanade, Jordan, North Monashee, North Selkirk, Shuswap, Badshot-Battle, Central Selkirk, Goat, Gold, Kokanee, North Okanagan, Retallack, Valhalla, Whatshan.

Increased southerly winds combined with recent storm snow may form new wind slabs at treeline and above.

Rider-triggered avalanches are possible.

Confidence

Moderate

Avalanche Summary

On Tuesday, numerous storm and wind slab avalanches were reported up to size 1.5. These failed naturally and were human-triggered. Additionally, several natural size 2 avalanches were seen on east-facing aspects near 2400 m and surface hoar was the suspect failing layer.

On Monday, natural solar-induced slab avalanches were reported up to size 2.5 and the recent storm snow continued to be reactive to rider triggering up to size 1.5. Reports indicate that the Selkirks seem to be the most reactive with rider remote-triggered slabs in the upper 50 cm of snow. These are failing on a surface hoar layer buried near the end of March or a crust on solar aspects. These avalanches were primarily on north and east aspects from 1700 m to 2200 m.

This MIN Report from Sunday indicates what is mentioned above.

Snowpack Summary

At higher elevations, 15-40 cm of mostly soft storm snow is settling over a widespread, crust except for 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 50 cm) was surprisingly reactive to human triggers in the Selkirks on Monday, especially on northeasterly slopes from 1700 m to 2100 m.

Forecast moderate to strong southwest wind will likely 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

Wednesday Night

Clear periods. Ridgetop wind 15 km/h from the southwest and freezing level falling to valley bottom. Treeline low around -9°C.

Thursday

Cloudy. Possible trace of snow. Ridgetop wind 15-35 km/h from the southwest. Freezing level rising to 1700 m. Treeline high around -3°C.

Friday

Cloudy with new snow 5-15 cm. Ridgetop wind 25-40 km/h from the southwest. Freezing level rising to 1900 m.

Saturday

Cloudy with possible sunny periods and flurries up to 5 cm. Ridgetop wind 15 km/h gusting to 50 km/h from the southwest. Freezing level 700 m in the morning, rising to between 1700 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

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.