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Avalanche Forecast

Archived

Dec 14th, 2020–Dec 15th, 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, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

North Columbia.

Triggering avalanches may become more likely throughout the day as new snow piles up. Watch for signs of instability such as whumphing, cracking and recent avalanches.

Confidence

Moderate - Uncertainty is due to the limited number of field observations. Uncertainty is due to extremely variable snowpack conditions reported through the region.

Weather Forecast

MONDAY NIGHT - Cloudy with scattered flurries, up to 5 cm / light southwest wind / alpine low temperature near -10 

TUESDAY - Cloudy with flurries, 5-10 cm with another 5-10 cm overnight / southwest wind, 20-40 km/h / alpine high temperature near -6 

WEDNESDAY - Mainly cloudy with flurries, 5 cm / southwest wind, 20-50 km/h / alpine high temperature near -7 

THURSDAY - Cloudy with flurries, 5-10 cm / southwest wind, 20-40 km/h / alpine high temperature near -7

Avalanche Summary

There have been a few recent reports of small avalanches above the recently buried surface hoar and crust layers. These include several dry loose avalanches in steep terrain, some small naturally triggered slab avalanches on solar aspects, and a few size 1 skier triggered avalanches in the Selkirks. The skier triggered avalanches were 30-40 cm thick (see the photo in this MIN report). 

While these avalanches have limited destructive potential, we anticipate this developing into a more concerning problem with the arrival of more snow.

Snowpack Summary

Up to 15 cm of snow is expected between Monday night and Tuesday afternoon, bringing totals up to 15-50 cm of snow now sitting on a weak layer that was buried about a week ago. 

This weak layer is variable, in some areas exists as a layer of feathery surface hoar, while in other areas it exists as a crust - either a sun crust on south facing slopes, or a melt-freeze crust at lower elevations.

In western and southern parts of the regions (e.g. the Monashees and Revelstoke area), the melt-freeze crust has been reported to extend into the alpine, with about 5-15 cm of fresh snow above it. Further east and north, 25-50 cm of snow likely sits on the surface hoar layer.

The primary concern is for any area where 30+cm of snow sits on top of the weak layer, regardless of whether it is surface hoar or a crust.

Another buried crust can be found in the lower snowpack (50-150 cm deep) with some reports of weak snow around this crust. There have been no recent avalanches reported on this layer, however occasional test results indicate that it may be reactive to human triggers on shallow rocky features at upper elevations.

Terrain and Travel

  • Investigate the bond of the recent snow before committing to your line.
  • Look for signs of instability: whumphing, hollow sounds, shooting cracks, and recent avalanches.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

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.