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Avalanche Forecast

Archived

Feb 19th, 2021–Feb 20th, 2021

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

Regions

South Coast.

Avalanche danger is progressively increasing as snow accumulates over the weekend. Stick to lower angle terrain on Saturday and prepare to back off if the storm arrives early.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

FRIDAY NIGHT: Scattered flurries with 5-10 cm of snow, light wind with moderate southwest gusts, treeline temperatures around -3 C.

SATURDAY: Cloudy with isolated flurries and up to 5 cm of snow, light wind with moderate southwest gusts, treeline temperatures around -3 C.

SUNDAY: Heavy snow starting Sunday evening with 20-30 cm of snow by the morning then another 10-20 cm of wet snow throughout the day with rain at lower elevations as the freezing level climbs to 1400 m, strong southwest wind, treeline temperatures reach +2 C in the afternoon.

MONDAY: The storm continues with another 30-50 mm of rain below 1400 m (and potentially lots of snow in the alpine), strong southwest wind, treeline temperatures around +1 C.

Avalanche Summary

There were some preliminary reports of dry loose avalanches reactive to skiers in the North Shore mountains on Friday, as more snow accumulates we will expect to see reactive storm slab avalanches in steep terrain.

Otherwise, the last notable avalanche activity was on Monday when there were numerous size 1-1.5 human triggered avalanches during an active storm slab event.

Snowpack Summary

Light flurries and wind on Saturday will add to the 20 cm of snow that fell Thursday night. There have been some reports of a thin freezing rain crust in this new snow. The 20 cm of new snow sits above crusts and hard wind affected snow in most areas. A mix of soft and hard layers can be found roughly 50-70 cm deep, including some faceted snow, a thin breakable crust, and isolated pockets of surface hoar. This all sits above a hard crust. While avalanches this weekend are most likely going to fail in fresh storm snow layers, there is a remote possibity for these deeper layers to also become reactive.

See the latest video from North Shore Rescue.

Terrain and Travel

  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
  • Closely monitor how the new snow is bonding to the old surface.

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.