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Avalanche Forecast

Archived

Mar 8th, 2021–Mar 9th, 2021

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

Regions

Lizard-Flathead.

Buried weak layers remain possible to be triggered, where they exist. Cornices and sun-exposed slopes will deteriorate during the heat of the day, potentially increasing the likelihood of avalanche activity.

Confidence

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

Weather Forecast

MONDAY NIGHT: Clear skies, 10 km/h northeast wind, alpine temperature -6 C.

TUESDAY: Morning clear skies and afternoon clouds, 20 km/h southwest wind, alpine temperature -6 C, freezing level rising to 1500 m.

WEDNESDAY: Morning clear skies and afternoon clouds, 20 km/h southwest wind, alpine temperature -6 C.

THURSDAY: Cloudy with snowfall, accumulation 5 to 10 cm, 20 km/h southwest wind, alpine temperature -6 C.

Avalanche Summary

No avalanches were observed on the weekend or Monday, besides some small loose avalanche out of steep terrain. The most recent persistent slab avalanche activity was on Friday, being triggered by explosives.

Snowpack Summary

A few centimetres of snow overlies a melt-freeze crust in many areas, with the exception being on north aspects above around 1700 m. Wind slabs may still exist on northerly aspects at alpine and treeline elevations. On solar aspects and below the freezing level, the snow may moisten during the heat of the day.

Up to 50 cm of snow sits above a variety of old interfaces that formed in mid-February. There is 60 to 100 cm sitting on a persistent weak layer that was buried in late January. These interfaces are mostly made up of sugary faceted grains, hard wind pressed snow, feathery surface hoar in wind-sheltered locations, and a melt-freeze crust on steep solar aspects. Periodic avalanches continue to be triggered on these layers. Check out this MIN for photos of the positioning of the layers in the snowpack.

Terrain and Travel

  • Be aware of the potential for large avalanches due to the presence of a persistent slab.
  • Pay attention to cornices and give them a wide berth when traveling on or below ridges.
  • Avoid exposure to steep, sun exposed slopes, especially when the solar radiation is strong.
  • Be careful with wind loaded pockets, especially near ridge crests and roll-overs.
  • When a thick, melt-freeze surface crust is present, avalanche activity is unlikely.

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.

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.