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Avalanche Forecast

Archived

Feb 14th, 2018–Feb 15th, 2018

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

Regions

Northwest Inland.

Wind and new snow have created touchy slabs at higher elevations. With buried weak layers in the snowpack a release near the surface has the potential to step down. Choose conservative terrain, avoid windloaded areas and be aware of overhead hazard.

Confidence

Moderate - Forecast snowfall amounts are uncertain on Thursday

Weather Forecast

THURSDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind moderate to strong west. Temperature -10. Freezing level valley bottom.FRIDAY: Mix of sun and cloud. Ridge wind becoming light, southwest. Temperature -10. Freezing level valley bottom.SATURDAY: Mostly cloudy, flurries. Accumulation 5 cm. Ridge wind moderate to strong, east. Temperature -15. Freezing level valley bottom.

Avalanche Summary

There have been no new reports of avalanches since the long weekend when we received reports of continued natural wind slab activity near Smithers. See this MIN report for the latest. On Saturday we received several reports of natural avalanches to size 3 (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. Also on Saturday, explosives control produced size 2.5 avalanches in below tree line terrain north of Smithers. Farther south but also below treeline, skiers were able to trigger a 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

About 10-20 cm of new snow and strong winds from a wide range of directions (mostly northwesterly) have scoured some slopes and created touchy wind slabs at tree line and above. Where the wind has not affected the snow, you'll find 50-80cm of recent storm snow from the past week. 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 produced sudden results in snowpack tests and have been the suspected weak layer in large remotely (from a distance) triggered avalanches.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.