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Avalanche Forecast

Archived

Jan 30th, 2015–Jan 31st, 2015

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

Regions

Kootenay Boundary.

A strong melt-freeze crust has developed on all but the highest elevation shaded aspects.

Confidence

Good

Weather Forecast

Freezing level dropping to valley bottoms overnight and not expected to rise above 600 metres on Saturday, or for the rest of the forecast period. Northwest winds developing on Saturday as cloud and very light precipitation move into the region from the coast. There is a chance of a sunny break on Saturday afternoon. 5-10 cm of snow is expected on Sunday combined with strong Westerly winds. Expect a break in the precipitation during the day on Monday, followed by another 5-10 cm of snow on Monday night combined with strong Southwest winds.

Avalanche Summary

There are no new reports of avalanches. The large (size 3.5) natural avalanche reported earlier in the week from the SE aspect of Mt Ymir was found to have released on the mid-December DPWL (deep persistent weak layer) rather than the mid-January PWL (persistent weak layer) that we initially thought was the sliding layer.

Snowpack Summary

Overnight freezing down to valley bottoms has created supportive melt-freeze crusts that have been reported on all aspects up to about 2400 metres. A new layer of surface hoar has been reported to be developing. The top 5-10 cm of surface snow has been moist during the day due to strong solar radiation. The mid-January weak layer of buried surface hoar is down about 20-50 cm and continues to give planar results in snow profile tests. The mid-December crust/facet/surface hoar layer is down 50 cm in low snowpack areas and down about 100 cm in deeper snowpack areas.

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.