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Avalanche Forecast

Archived

Feb 6th, 2021–Feb 7th, 2021

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

South Coast Inland.

In the north of the region the main concern is wind slabs at upper elevations. In the south, the main concern is deep storm slabs and loose dry sluffing in the new snow. See the problems tab for more details.

Confidence

Moderate - Recent weather patterns have resulted in a high degree of snowpack variability within the region.

Weather Forecast

Saturday night: Flurries, around 5 cm in the north and snow up to 15 cm in the south, moderate northwest ridgetop wind easing to light, alpine temperature -10, freezing level dropping to valley bottom.

Sunday: Mix of sun and cloud with flurries, up to 10 cm in the south, light northwest ridgetop wind, alpine high -10.

Monday: Sunny, light variable ridgetop wind, alpine high -14.

Tuesday: Mix of sun and cloud, light northerly ridgetop wind, alpine high -17.

Avalanche Summary

Skier triggered wind and storm slabs up to size 1 were reported on Thursday and Friday throughout the region. Last week there were reports of natural, explosive and human triggered avalanches size 1-2, including a widespread natural avalanche cycle Monday night. Many of these failed on the recently buried persistent weak layer.

Snowpack Summary

Snowfall in the south of the region is forecast to conclude today with a nice even blanket of low density snow as temperatures drop and winds die down. In the north, localized areas of soft wind slab may sit over a crust on solar aspects. Recent variable wind directions have resulted in wind loading in atypical terrain features.

30-80 cm of recent snow sits on a persistent weak layer that consists of facets at upper elevations, surface hoar in sheltered areas, a melt-freeze crust below 1600 m, and a sun crust on south-facing slopes. 

In the south, the underlying snowpack is well consolidated. In the north, a melt-freeze crust from early December may be found 100 to 200 cm deep. Recent reports suggest that this layer is gaining strength and it has been unreactive in recent weeks.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be careful as you transition into wind affected terrain.
  • Be aware of the potential for large avalanches due to the presence of a persistent slab.

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.

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.