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Avalanche Forecast

Archived

Dec 5th, 2018–Dec 6th, 2018

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, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

North Columbia.

The snowpack is gaining strength, but keep the persistent slab in mind when choosing terrain. Be sure to make high quality snowpack observations before pushing into more committing terrain.

Confidence

Moderate - Due to the number of field observations

Weather Forecast

WEDNESDAY NIGHT - Cloudy with clear periods / light southerly winds / alpine low temperature near -11THURSDAY -Sunny with cloudy periods / light southeast winds / alpine high temperature near -7FRIDAY - Sunny with cloudy periods / light to moderate  south winds / alpine temperature steady  near -7SATURDAY - Cloudy with sunny periods and isolated flurries / light to moderate south winds / alpine high temperature near -6, low temperature near -8

Avalanche Summary

No new avalanches have been reported in the region.Although outside of the region, it is notable that three large avalanches have been reported recently in the South Columbia region between November 24 and December 1. It is likely that they ran on the October crust as they were essentially full depth avalanches. One occurred naturally, one was human triggered and the other was triggered with explosives.We currently have very few observations from within this region. Please post your observations to the Mountain Information Network (MIN).

Snowpack Summary

The primary concern in the snowpack is a layer of surface hoar (weak feathery crystals) and sun crust on steeper south facing slopes. This weak layer is down 30-50 cm and it is most prominent at treeline, but it may be found in sheltered alpine areas.At the base of the snowpack is a crust that formed in late October. Steep, rocky alpine terrain, with a shallow snowpack are the most likely areas to trigger this layer. It would likely take a large load such as a cornice fall to produce an avalanche on this layer, but the consequences are high as it would result in a large, full depth avalanche.Total snowpack depths vary greatly with elevation. Recent reports show depths of 120-230cm in the alpine, 90-180 cm at treeline and 10-120 cm below treeline.

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.