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Avalanche Forecast

Archived

Jan 19th, 2015–Jan 20th, 2015

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

Regions

Little Yoho.

Parks Canada is planning Avalanche Control on Mt. Dennis for Tuesday January 20. No ice climbing or travel in this area please. TH

Weather Forecast

Temperatures should cool, and skies should clear as the winds shift to the NW Tuesday under the influence of a high pressure system. A series of lows will be pushed well North as a result of this high but clouds should return mid day Wednesday with increasing winds, a chance of light snow arriving overnight, and temperatures rising into Thursday.

Snowpack Summary

15 to 25cm of recent snow with west winds has created slabs on facets, surface hoar, sun crust on steep South slopes and hard windslabs along ridge crests Treeline and above. The Dec 18 surface hoar layer is down 50 to 60 cm. This layer is very prominent and has been producing moderate test results and whumpfing on past field trips.

Avalanche Summary

On an avalanche control flight today to the Sunshine road, 8 of 9 shots produced significant avalanches and 3 natural avalanches were observed. Most of these initiated in the recent storm slabs 20 cm deep but several also stepped down to the Dec 18 interface to a depth of 50cm. Two size 1.5 naturals were observed on Labbat's Lane and Pilsner Pillar

Confidence

Due to the number and quality of field observations

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.