Avalanche Forecast

Archived

Jan 15th, 2020–Jan 16th, 2020

Alpine

Natural avalanches possible, human triggered probable.

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.

New wind slabs will form at higher elevations on Thursday, requiring careful route finding.

Confidence

High - The number, quality, or consistency of field observations is good, and supports our confidence.

Weather Forecast

WEDNESDAY NIGHT: 5-15 cm of low density snow, strong wind from the south, alpine temperatures around -20 C.

THURSDAY: Flurries with 5-15 cm of low density snow, moderate to strong wind from the southwest, alpine high temperatures around -12 C.

FRIDAY: Light flurries with mix of sun and cloud, light wind from the southwest, alpine high temperatures around -12 C.

SATURDAY: Light flurries with 5-10 cm of snow, moderate wind from the southwest, alpine high temperatures around -10 C.

Avalanche Summary

Avalanche activity has quieted down over the past few days, but incoming weather will refresh the wind slab problem on north and east lee features. Last weekend there were a few notable reports of large persistent slab avalanches in the Selkirks and the northern tip of the Monashees (near Blue River and Valemount). The avalanches failed on a 100 cm deep surface hoar layer on north and east aspects between elevations of 1200 to 2100 m. Recent observations suggest this layer has trended towards being less reactive under the current conditions.

Snowpack Summary

Surface conditions are variable due to cold temperatures and shifting wind directions over the past few days, but expect fresh wind slabs to form on lee features on Thursday. A layer of surface hoar is now buried 80-150 cm below the surface and continues to be a concern certain parts of the Selkriks and the northern end of the Monashees. A facet/crust layer from late November lingers near the bottom of the snowpack and has occasionally been reactive in isolated shallow snowpack areas.

Terrain and Travel

Be carefull around freshly wind loaded features.
Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

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.