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Avalanche Forecast

Archived

Jan 2nd, 2020–Jan 3rd, 2020

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

North Columbia.

Snowfall through Thursday night and Friday combined with wind and warm temperatures will keep the avalanche danger at High on Friday.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Thursday Night: Snow, accumulation 10-20 cm . Alpine temperature -10 C. Moderate northwest wind.

Friday: Snow, accumulation 10-15 cm. Alpine temperature -5 C. Moderate to strong west wind. Freezing level 1400 m.

Saturday: Snow, accumulation 10-15 cm. Alpine temperature -6 C. Moderate to strong southwest wind. Freezing level 1200 m.

Sunday: Flurries. Alpine temperature -6 C. Moderate southwest wind. Freezing level 1000m.

Avalanche Summary

There was a widespread natural storm slab avalanche cycle to size 2.5 on Wednesday. Avalanches were 30-60 cm deep and were reported on all aspects and elevations. Additionally there were several human triggered avalanches reported up to size 2. Some of these were remotely (from a distance) triggered.

Snowpack Summary

Expect another 10-20 cm of new snow overnight Thursday to add to the 40-70 cm that fell through the New Year's period. All this recent snow has buried a layer of surface hoar found at all elevations. In some places the surface hoar may be combined with sun crust on steep sun-exposed aspects.

A weak layer that was buried at the end of December is now approximately 100 cm deep and may present as surface hoar in sheltered areas, sun crust on steep solar aspects and/or a melt freeze crust below 1700 m.

An additional layer of surface hoar buried mid December is 110-180 cm deep. Avalanche activity on this layer has tapered off, but there is still concern for heavy loads to step down to this layer. A crust from late November is now over 180 cm deep. Concern for this layer is limited to rocky or variable snowpack depth areas in the alpine where it most likely exists as a combination of facets and crust.

Terrain and Travel

  • Minimize exposure during periods of heavy loading from new snow and wind.
  • Avoid freshly wind loaded terrain features.
  • Storm slabs in motion may step down to deeper layers resulting in large avalanches.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Storm slab size and sensitivity to triggering will likely increase through the day.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.