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Avalanche Forecast

Archived

Mar 3rd, 2021–Mar 4th, 2021

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

Regions

South Columbia.

Warm temperatures and sunshine will elevate avalanche conditions, especially on south-facing slopes. Stick to low angle shaded terrain.

Confidence

Moderate - Uncertainty is due to how the snowpack will react to the forecast weather.

Weather Forecast

A ridge of high pressure brings dry, warm, and sunny weather.

WEDNESDAY NIGHT: Clear skies, light south wind, treeline temperatures drop to -3 C.

THURSDAY: Sunny, light south wind, freezing level climbs to 2100 m with treeline temperatures around +1 C.

FRIDAY: Mix of sun and cloud, moderate south wind, freezing level climbs to 1800 m with treeline temperatures around -1 C.

SATURDAY: Cloudy with scattered flurries and 5-10 cm of new snow, light southwest wind, freezing level climbs to 1500 m with treeline temperatures around -3 C.

Avalanche Summary

On Thursday the primary concern is natural avalanches on steep sun-exposed slopes. These will most likely present as wet loose avalanches, but larger wind and persistent slab avalanches are also possible. Read the latest Forecaster Blog for concerns about the warming.

Since the weekend, avalanche activity has primarily been limited to small (size 1) wind slab and dry loose avalanches on a variety of aspects. There have been a few reports of sporadic persistent slab avalanches in the past month failing on the late January persistent weak layer. While this layer is trending towards being unreactive, the current warming trend could temporarily heighten the likelihood of avalanches on this layer. 

Snowpack Summary

Rising freezing levels and sunshine will be melting, and potentially destabilizing, snow surfaces the next few days. Higher elevations have been impacted by recent wind from the southwest, likely leaving wind slabs lurking on shaded north and east slopes.

The lower snowpack has been strengthening with reactivity on persistent weak layers on the decline. The two layers of concern have been a layer of facets that was buried in mid-February (60-100 cm deep) and a layer of surface hoar and/or crusts that was buried in late January (80-120 cm deep). The impulse of warming over the next few days will likely be the final test on these layers, as there is some uncertainty about whether they will become reactive with warming temperatures.

Terrain and Travel

  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.
  • The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
  • Expect slab conditions to change drastically as you move into wind exposed 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.