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Avalanche Forecast

Archived

Jan 28th, 2017–Jan 29th, 2017

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

Little Yoho.

With elevated winds, we are seeing isolated natural avalanches that are hard to predict. Be suspect of slopes where a slab sits over the weaker layers below, and watch how any winds are loading alpine features. SH

Weather Forecast

Alpine temperatures in the -5 to -9 range for Sunday and strong West winds (up to 100kmh). 5 cm is currently forecast for Sunday evening. Cooler temperatures for Monday.

Snowpack Summary

In many areas, a generally weak snowpack exists until 2000-2200m . At 2000m, there is generally 135cm of snow, with the Jan 17 surface hoar layer down 25cm producing sudden planar test results - but minimal slab formation above. In the mid-pack, the Dec facets are 20cm thick, and near the ground some weak facets sit just below on old ice crust.

Avalanche Summary

A 300m fracture line was seen yesterday on Cathedral Peak which was 50cm deep on a N-NE aspect at treeline/low alpine. Wind loading from yesterday was the suspected culprit.  East of the divide new reactive wind slabs were reported in the alpine, and this is likely in Little Yoho as well.

Confidence

Timing, track, or intensity of incoming weather system is uncertain on Sunday

Problems

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.

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.