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Avalanche Forecast

Archived

Mar 5th, 2019–Mar 6th, 2019

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

Kootenay Boundary.

Wind slabs may be reactive in the alpine. The persistent slab problem still exists at lower elevations and is best controlled by diligent group management and terrain travel.

Confidence

High -

Weather Forecast

TUESDAY NIGHT: Increasing clouds, moderate southeast wind, alpine temperature -7 C.WEDNESDAY: Cloudy with light snowfall, trace accumulation, light to moderate southeast wind, alpine temperature -9 C.THURSDAY: Cloudy with snowfall, accumulation 10 cm, moderate southwest wind, alpine temperature -10 C.FRIDAY: Cloudy with light snowfall, accumulation 1 to 3 cm, light to moderate northwest wind, alpine temperature -10 C.

Avalanche Summary

Small (size 1) wind slab avalanches were reported on Monday, being triggered by skiers.Also on Monday, a small (size 1) persistent slab avalanche was triggered by a skier. It released on the mid-February layer described in the Snowpack Summary. It was between 20 and 50 cm deep, on a south aspect, and at 2100 m. Similar avalanches have been triggered recently, such as this one.

Snowpack Summary

Strong east wind has scoured the snow surface in exposed terrain and produced wind slabs in lee and cross-loaded terrain features. In sheltered areas, soft snow may still be found. A melt-freeze crust likely prevails on southerly slopes.Two layers of weak and feathery surface hoar crystals are buried in the snowpack between 40 and 80 cm deep, which were buried mid-February and early-February. The layers may be associated with a melt-freeze crust on southerly aspects. These layers remain reactive in snowpack tests and have produced sporadic avalanches in the region over the past week.

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.