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Avalanche Forecast

Archived

Feb 11th, 2018–Feb 12th, 2018

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

Regions

Northwest Inland.

Strong winds have created touchy slabs at higher elevations. Be wary of persistent slabs lurking at lower elevations. Choose conservative terrain and be aware of overhead hazard, especially on sunny aspects.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

MONDAY: Increasing cloud in the afternoon. Ridge wind strong from the northwest. Temperature -10. Freezing level valley bottom with an above freezing layer between 1400m and 1900m.TUESDAY: Snow (5-10cm). Ridge wind strong, southwest. Temperature near -4. Freezing level 400 m.WEDNESDAY: Mostly sunny. Ridge wind moderate to strong from the north / west. Temperature -7. Freezing level valley bottom.

Avalanche Summary

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

Strong north west winds picked up on Saturday, redistributing last week's storm snow and creating touchy wind slabs at higher elevations. A strong inversion also set up with tree line temperatures near 0 degrees and a thin crust formed on steep south facing slopes.Wednesday's storm delivered between 15-50 cm of new snow, bringing totals to 40-100 cm over the past week. Areas near Smithers and farther south saw higher snowfall amounts than areas to the north. 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 ine elevations. Recent 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 recent snowpack tests and have been the suspected weak layer in recent large remotely (from a distance) triggered avalanches.

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.