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Avalanche Forecast

Archived

Mar 16th, 2022–Mar 17th, 2022

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

Regions

North Columbia.

Practice good travel habits and choose conservative, low consequence lines. A buried weak layer has been reactive in recent days, creating large and surprising avalanches.

Make sure to read the Avalanche Problems section.

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast.

Weather Forecast

A series of frontal systems coming in off the coast will bring light precipitation throughout the week.

Wednesday Overnight: Partially cloudy, light snowfall, up to 5 cm of accumulation. Freezing level dropping to 500 m. Moderate to strong southwest winds. 

Thursday: Cloudy with snowfall, 5-15 cm of accumulation. Freezing level rising to 1500 m. Moderate to strong southwesterly winds. 

Friday: Partially cloudy, light flurries. Freezing level rising to 1500 m in the afternoon. Light to moderate southwesterly winds.

Saturday: Mainly cloudy, light flurries. Freezing level around 1000 m. Light to moderate southwesterly winds. 

Avalanche Summary

On Tuesday, numerous natural and skier-triggered storm slabs were reported throughout the region. The larger and more consequential avalanches occurred in wind-loaded terrain or on the weak layer of surface hoar or crust below. 

A natural avalanche cycle up to size 3 occurred on Monday afternoon with heavy snowfall, wind and warm temperatures.

Snowpack Summary

Continued light precipitation will add to 30-60 cm of recent settling storm snow at treeline and above. Storm snow tapers rapidly below treeline, where moist snow or a melt-freeze crust can be expected from rain and warm temperatures.

This new snow is sitting on various surfaces, including hard wind-affected snow, sun crusts on southerly slopes, facetted snow, and isolated pockets of surface hoar. The new snow is bonding poorly to this old surface, especially where a facet/crust layer or surface hoar is present below.

The late February persistent weak layer combination of crust, facets and surface hoar is down 30-40 cm. Reports suggest this layer is not a problem in most areas. Two persistent weak layers from mid-February and late January are buried 50-120cm deep. No recent avalanches have been reported on these layers.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Be especially cautious as you transition into wind affected terrain.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

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.

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.