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Avalanche Forecast

Archived

Jan 13th, 2022–Jan 14th, 2022

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

Regions

Sea To Sky.

High elevations hold dry snow seeing warming for the first time. Watch for signs of instability, moist surface snow and new natural avalanches. 

Avoid large unsupported slopes, deeply buried weak layers remain a concern. 

Confidence

Moderate - Uncertainty is due to how quickly the snowpack will recover and gain strength. Uncertainty is due to rapidly fluctuating freezing levels.

Weather Forecast

Freezing levels continue to change rapidly in the wake of the storm, reaching peak elevations on Friday and likely again on Sunday.

THURSDAY NIGHT: Partly cloudy with no precipitation expected. Freezing levels rise to 2500 m with light westerly winds.

FRIDAY: A mix of sun and cloud with isolated flurries expected. Winds return to strong southwest. Freezing levels drop from 2500 m to 1500 m in the morning.

SATURDAY: Cloudy with isolated flurries. Freezing levels stay below 1500 m. Strong westerly winds. 

SUNDAY: Mostly cloudy with light snow. Increasing westerly winds. Freezing levels around 1500 m. 

Avalanche Summary

Heavy precipitation and warm temperatures produced widespread natural avalanche cycles at all elevations. At treeline and below saw a loose wet avalanche cycle to size 3 on all aspects, during the most intense rain and warming. Upper treeline and alpine terrain produced a storm slab cycle to size 3 in most areas. 

A size 4 avalanche was naturally triggered near Harrison Lake. This was thought to have started as a cornice fall which triggered a storm slab and stepped down to a deeper weak layer, up to 3 m deep in places. 

Snowpack Summary

Heavy precipitation over the last week has created a variety of surface snow conditions. Strong southwest winds have created pockets of dry snow at alpine elevations on north through east facing slopes. Precipitation fell as wet snow or rain below 2200m, creating saturated snow that is forming a melt freeze crust with moist snow below. 

A crust that formed prior to the rain was observed up to 2000m. This is now buried up to 30 cm deep and may be breaking down at lower elevations where rain had a greater impact. 

Two buried weak layers of sugary, faceted grains sit in the middle and lower snowpack, at 100cm deep and 150-250 cm deep. The deeper layer was formed by heavy rain followed by a cold spell in early December. It is most prominent between 1700 and 2100 m. Avalanches on this layer are large, but sporadic and isolated. The most likely place to trigger it would be in thin, rocky snowpack areas. The lower snowpack is well-settled and strong.

Terrain and Travel

  • A moist or wet snow surface, pinwheeling and natural avalanches are all indicators of a weakening snowpack.
  • Back off slopes as the surface becomes moist or wet with rising temperatures.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Be careful as you transition into wind affected terrain.

Problems

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.

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.