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Avalanche Forecast

Archived

Mar 21st, 2022–Mar 22nd, 2022

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

Regions

North Rockies.

New slabs may form up high. There's uncertainty in how Tuesday's warming will impact the snowpack. Best to adopt a conservative mindset and dial back your terrain choices.

Confidence

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

Weather Forecast

MONDAY NIGHT: Cloudy with no precipitation, 40 km/h southwest wind, alpine temperature -4 C, freezing level 1500 m.

TUESDAY: Morning snowfall then mix of sun and clouds, accumulation 5 to 10 cm with up to 30 cm possible in the north, 60 to 80 km/h southwest wind, alpine temperature 1 C, freezing level rising to 2400 m.

WEDNESDAY: Cloudy with rain switching to snow, accumulation 10 to 20 cm snow above the rain-snow line, 40 to 60 km/h west wind, alpine temperature 0 C, freezing level 2000 m dropping to 1400 m.

THURSDAY: Clear skies with no precipitation, 10 km/h southwest wind, alpine temperature -6 C.

Avalanche Summary

A few wind slabs were observed in the region on Sunday, being small to large (size 1 to 2) and on variable aspects. No other avalanches were observed.

Looking forward, avalanche activity may pick up on Tuesday into Wednesday with a rise in the freezing level. There's uncertainty in exactly what the warming will do to the snowpack, so adopting a conservative mindset will be important.

Snowpack Summary

5 to 10 cm of snow is forecast for Tuesday, with locally higher amounts possible in the north. The snow will fall with strong southwest wind, forming wind slabs in lee terrain features in wind-exposed terrain. The storm is also coming with warm air, raising the freezing level to around 2400 m by the late afternoon. There's uncertainty in what this warming will do, but it has the potential of destabilizing the snowpack and triggering avalanches.

A weak layer may be found around 40 to 80 cm deep in the western half of the region. The layer consists of surface hoar crystals in treeline terrain in areas sheltered from the wind and otherwise a hard melt-freeze crust associated with weak faceted grains on sun-exposed slopes. Check out this blog for more information. This layer hasn't shown reactivity since last week but may still linger in portions of the region.

The remainder of the snowpack is well-bonded.

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • As surface loses cohesion due to melting, loose wet avalanches become common in steeper terrain.
  • If triggered loose wet avalanches may step down to deeper layers resulting in larger avalanches.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.

Problems

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.

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.