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

Regions

North Columbia.

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: Up to 10 cm of snowfall possible overnight. Moderate southwesterly winds. Freezing levels drop to 500 m. 

FRIDAY: Scattered flurries continue with mostly cloudy skies. Moderate southwesterly winds. Freezing levels rise to 1500 m. Alpine high of -1.

SATURDAY: Scattered flurries with mostly cloudy skies, 5 cm possible over the day. Moderate southwesterly winds. Freezing levels rise to 1700 m. Alpine high of +1.

SUNDAY: 5-10 cm possible overnight. A mix of sun and cloud with moderate northwesterly winds. Light westerly winds. Freezing levels around 1300 m, alpine high of -3. 

Avalanche Summary

Reports from Wednesday continue to indicate a reactive and unstable snowpack. 

  • Several natural slab avalanches up to size 2 were reported within the most recent 25 cm of storm snow.
  • Numerous human triggered avalanches were also reported, with several remotely triggered avalanches occurring on the buried weak layers of surface hoar, facets and crust. Activity mainly occurred on south and east facing slopes around treeline, producing avalanches up to size 2.5.

On Tuesday, numerous natural and human triggered avalanches were reported on these same layers.

Snowpack Summary

40-60 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 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 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.
  • Potential for wide propagation exists, fresh slabs may rest on surface hoar, facets and/or crust.
  • Avoid freshly wind loaded features, especially near ridge crests, roll-overs and in steep terrain.
  • If triggered, wind slabs avalanches may step down to deeper layers resulting in larger avalanches.

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.