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Avalanche Forecast

Archived

Feb 16th, 2018–Feb 17th, 2018

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

Regions

Northwest Inland.

Wind and recent storm snow have created slabs at upper elevations. Reactivity of these may increase if the sun starts to pack a punch on solar aspects.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

SATURDAY: Mix of sun and cloud. Ridge wind moderate to strong, northeast. Temperature -16. Freezing level valley bottom.SUNDAY: Mostly sunny. Ridge wind, moderate, northeast. Temperature -15. Freezing level valley bottom.MONDAY: Mostly sunny. Ridge wind moderate, northwest. Temperature -10. Freezing level valley bottom.

Avalanche Summary

There have been no new reports of avalanches since Wednesday when widespread natural avalanche activity up to size 2 was reported on wind-loaded, leeward slopes as well as loose snow releases on steep solar aspects in the afternoon.Last weekend when we received reports of continued natural wind slab activity near Smithers. See this MIN report from Sunday.Also from last weekend, several natural avalanches up to size 3 were reported (particularly on northeast facing slopes at higher elevations) as the winds picked up and slab avalanches ran surprisingly far. See this MIN post for more information. See here for a stunning photo of a large avalanche. This included a skier triggered size 2 persistent slab avalanche on a south facing sparsely treed (deciduous) slope just north of Hankin. See here for the MIN report.

Snowpack Summary

Winds (mostly northwesterly) have scoured wind-exposed slopes and created wind slabs up to 50 cm thick on leeward slopes at tree line and above. In areas sheltered from the wind, you'll find 30-50 cm of settled storm snow. A crust and/or weak feathery surface hoar layer buried in mid-January now lies about 100 cm below the surface. The crust exists well into the alpine and the surface hoar can be found in sheltered areas in the lower alpine and tree line elevations. Snowpack tests produced hard, sudden results on weak, sugary snow crystals associated with this crust in the Smithers area, indicating that this is still a layer of concern to watch for.Another two crust / surface hoar layers that were buried in December are now 100-150 cm below the surface. These layers have produced sudden results in recent snowpack tests and may still be sensitive to triggering from shallow snowpack areas.See here for a good summary of recent snowpack test results near Smithers.

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.