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Avalanche Forecast

Archived

Mar 17th, 2022–Mar 18th, 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 possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Cariboos.

Buried weak layers continue to be reactive to triggers. Stick to conservative terrain with minimal overhead hazard and watch for signs of instability like whumpfing, natural avalanches and cracking.

Find more information on this tricky layer here.

Confidence

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

Weather Forecast

THURSDAY NIGHT: Flurries continue, around 5cm of snow. Freezing levels drop to 500 m overnight. Moderate southwesterly winds. 

FRIDAY: Partly cloudy, with isolated flurries. Freezing level rising to 1500 m. Light to moderate southwesterly winds. Alpine high of -1.

SATURDAY: A mix of sun and cloud. Flurries continue, up to 5 cm of snow. Freezing levels rising to 1600 m. Moderate southwesterly winds. Alpine high of +1.

SUNDAY: Around 5 cm overnight. Mostly sunny with moderate northwest winds. Freezing levels reach 1200 m, alpine high of -3. 

Avalanche Summary

On Wednesday, natural activity was observed to size 2 in wind loaded features.

Several avalanches were reported on the buried weak layer of surface hoar or facets on a crust. Avalanches were naturally and remotely triggered (from a distance), and mostly occurred on south facing slopes around treeline. However of note, a size 3 was remotely triggered on a northeast aspect near McBride. While the layer of concern is only 40 cm deep, this produced a large avalanche with impressive propagation. 

On Tuesday numerous natural and human-triggered storm slabs were reported. These mainly occurred on north-facing (shaded) aspects in the alpine and treeline and failed on a buried weak layer of surface hoar. 

Snowpack Summary

30-60 cm of settling storm snow is being redistributed into wind loaded features at higher elevations. At lower elevations moist snow or a melt-freeze crust likely exists from recent 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, producing large avalanches within the last 3 days. 

The lower snowpack is generally well-settled and strong in most areas, with crust layers 50 to 100 cm deep.

Terrain and Travel

  • 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.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.

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.

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.