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Avalanche Forecast

Archived

Feb 15th, 2019–Feb 16th, 2019

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

Regions

North Columbia.

Until recently, this region was a hotspot for avalanche activity on two persistent weak layers within the snowpack. Despite the moderate hazard, a cautious approach to backcountry travel is recommended.

Confidence

High -

Weather Forecast

FRIDAY NIGHT: Around 5 cm of low density snow expected. Mostly light winds.SATURDAY: 2-4 cm new snow. Treeline temperatures around -8C. Light northeasterly winds.SUNDAY: Flurries. Treeline temperatures around -10C. Light northeasterly winds.MONDAY: Dry, with some clear spells. Treeline temperatures around -12C. Moderate northwesterly winds.

Avalanche Summary

On Wednesday and Thursday a few size 1-1.5 wind slab avalanches were triggered naturally and by skiers mostly in the alpine on a variety of aspects. Persistent slab avalanches have tapered off, with three events noted on northeast aspects between 1200 and 1900 m from Monday and Tuesday this week but none reported on Wednesday or Thursday. However, I'd remain leery of the mid- and late-January weak layers especially at treeline elevations.

Snowpack Summary

10-15 cm of recent low density snow sitting on the surface has been blown around by strong northeasterly winds, creating reverse-loading on some slopes. There are two prominent, touchy weak layers in the snowpack that have been responsible for a several dangerous avalanches in the past 2 weeks. The upper layer was buried at the end of January and lies approximately 40 cm below the surface. The lower one was buried mid-January and lies approximately 75 cm below the surface. Both comprise a mix of surface hoar and facets and may lie on top of a sun crust on southerly aspects. Both layers are potentially reactive and in any given location, one or both could potentially exist in the snowpack. Wide propagation has been noted, meaning avalanches have the potential to be large (up to size 3). These weak layers are most prevalent at treeline and below, but may also be found in sheltered areas in the alpine.Average snow depths are approximately 300 cm. Very sporadically, failures have occurred near the base of the snowpack in or close to this region. These releases have almost all been from high alpine areas, possibly triggered close to rocky features.

Problems

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.

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.