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Avalanche Forecast

Archived

Mar 19th, 2022–Mar 20th, 2022

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

Regions

South Columbia.

Conservative terrain choices are advised, buried weak layers still remain reactive on specific features. 

Expect avalanche danger to increase as the sun hits the snowpack. Triggering avalanches will become more likely on sun affected slopes. 

Confidence

Moderate - Uncertainty is due to the fact that persistent slabs are particularly difficult to forecast. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

SATURDAY NIGHT: 5-15 cm possible overnight. Higher accumulations around 15 cm may be seen north of Trout Lake. Moderate southwest winds. Freezing levels drop to valley bottom.

SUNDAY: Scattered flurries with a mix of sun and cloud. Moderate westerly winds. Freezing levels around 1400 m, alpine high of -3.

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

TUESDAY: Freezing levels only push higher, reaching 2500 m. A mix of sun and cloud. Light to moderate southwest winds, alpine high of +4. 

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. 

Reports indicate continued natural avalanche activity throughout the region within the last 3 days. Naturals were observed on Friday up to size 2 in north facing treeline features. Remotely triggered avalanches were reported to size 1, within the storm snow and on the crust buried on south facing slopes. 

A notable size 2.5 was triggered on a wind loaded feature on a northwest facing slope at 2100 m. This likely failed on the buried surface hoar.

Wet avalanche activity has been observed on south facing slopes during intense sunshine, and on all aspects below the freezing line throughout the week. 

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.