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Avalanche Forecast

Archived

Mar 20th, 2022–Mar 21st, 2022

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 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.

Regions

South Columbia.

Watch for reactivity on specific features - buried layers of surface hoar and crust are still surprising backcountry users. 

Understand how avalanche danger may change as you move through different aspects and elevations before planning your trip. 

Confidence

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

Weather Forecast

SUNDAY NIGHT: Scattered flurries. Light to moderate westerly winds. Freezing levels drop to valley bottom. 

MONDAY: Mostly cloudy with flurries, and light to moderate southwest winds. Freezing levels reach 1600 m, with alpine highs of 0.

TUESDAY: Freezing levels only push higher, potentially reaching 3000 m. A mix of sun and cloud. Light to moderate southwest winds, alpine high of +4. 

WEDNESDAY: Freezing levels drop to around 2000 m over the day. Moderate to strong southwesterly winds. Alpine high of 

Avalanche Summary

Overall reports indicate a gradual tapering of reactivity of the buried weak layers, however reactivity remains in specific features where these weak layers are more prominent. 

On Saturday numerous size 2 slab avalanches were human and naturally triggered. Avalanches varied from failing on recent storm snow interfaces to failing on the buried weak layers of concern. Activity mainly occurred at treeline elevations on northwest to south facing slopes. 

Loose wet avalanches were noted in some areas where freezing levels rose significantly or where strong sunshine affected the snowpack. 

Snowpack Summary

Up to 60 cm of recent settling storm snow sits over a layer of weak surface hoar in sheltered and shaded terrain, and over a crust on south facing slopes. Test results show that the new snow is bonding poorly to old surfaces in many areas, producing large avalanches within the last 3 days and reactive results on testing. 

At higher elevations consistent southwest winds are creating deeper deposits on north through east facing features. Below 1700 m, moist snow or a melt-freeze crust likely exists from recent rain and warm temperatures.

The late February persistent weak layer combination of crust, facets and surface hoar is down 70-90 cm. Two persistent weak layers from mid-February and late January are buried 100-170cm deep. Avalanches on these layers are unlikely to be triggered. 

Terrain and Travel

  • 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.
  • Minimize exposure to sun-exposed slopes when the solar radiation is strong.

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.