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Avalanche Forecast

Archived

Mar 17th, 2020–Mar 18th, 2020

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

Regions

Kootenay Boundary.

Little change is expected due to a stable weather pattern. Be extra cautious as slopes warm up throughout the day.

Confidence

High - We have a good understanding of the snowpack structure and confidence in the weather forecast

Weather Forecast

A high pressure system brings clear dry conditions for the week.

TUESDAY NIGHT: Clear skies, light north wind, freezing level drops to valley bottom, alpine temperatures drop to -8 C.

WEDNESDAY: Mostly sunny, light northwest wind, freezing level climbs to 1700 m in the afternoon, alpine temperatures reach -2 C.

THURSDAY: Mix of sun and cloud, light southeast wind, freezing level climbs to 1400 m in the afternoon, alpine temperatures reach -4 C.

FRIDAY: Sunny, light to moderate northwest wind, freezing level climbing 1700 m in the afternoon, alpine temperatures reach -2 C. 

Avalanche Summary

Recent avalanche activity has primarily been small (size 1-1.5) wet loose avalanches in steep south-facing terrain and a few wind slab avalanches in alpine terrain. Some of the wind slabs have been large (size 2.5-3), primarily on south and southeast facing slopes. Persistent slab avalanche activity has starting to quiet down. Over the past two weeks, only a few small to large (size 1-2) avalanches have released on the late February surface hoar layer. They have most often released between 1700 and 2100 m on northwest to east aspects.

Looking forward, daytime warming will create potential for loose avalanches on steep sun-exposed slopes and could increase the likelihood of wind and persistent slab avalanches.

Snowpack Summary

Surface conditions are highly variable with a mix of crusts, moist snow, and hard wind slabs. The surface will become moist on sun-exposed slopes and at lower elevations throughout the day. A few different layers of surface hoar and melt-freeze crust exist in the upper snowpack. This layers have produced some isolated avalanches over the past two weeks and remain possible to trigger. One layer was buried a week ago and may be found about 20 to 40 cm deep, but the most widespread layer was buried in late February and is now 40 to 80 cm deep. This layer is most commonly found in open trees (e.g. in this MIN). The remainder of the snowpack is strong and well-settled.

Terrain and Travel

  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
  • Approach steep open slopes at and below treeline cautiously, buried surface hoar may exist.

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.