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Avalanche Forecast

Archived

Mar 6th, 2022–Mar 7th, 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, 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

Northwest Inland.

Extreme west wind will continue to develop fresh wind slabs where loose snow is available for transport and grow cornices. It is uncertain whether the buried weak layer is reactive to human triggers. 

Confidence

Moderate - Uncertainty is due to the limited number of field observations.

Weather Forecast

Sunday night: Mostly cloudy, up to 2 cm snow, extreme west wind, alpine low -5 °C, freezing level dropping to 500 m. 

Monday: Mix of sun and cloud, trace of new snow, moderate northwest wind, alpine high -7 °C, freezing level around 800 m.  

Tuesday: Mainly sunny, light to moderate northeast wind, alpine high -12 °C, freezing level at valley bottom.

Wednesday: Mix of sun and cloud, moderate northerly wind, alpine high -8 °C, freezing level at valley bottom. 

Avalanche Summary

A large (size 2) slab avalanche that was likely triggered by a failed cornice was reported on Saturday. Small loose wet avalanches were reported on Friday. 

The field team reported two slab avalanches that had been triggered by cornices earlier in the week. Check out the MIN here. 

Snowpack Summary

40-60 cm of well settled and bonded snow sits on top of the mid-February crust. Though this layer has not produced avalanche activity, professionals in the area are still treating it with suspicion. The upper snowpack became moist below 1500 m with the recent warm temperatures and will now likely have a crust. Cornices are looming in alpine areas. 

The lower snowpack is well bridged by the mid-February crust and triggering avalanches below this layer is unlikely at this time. 

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Avoid exposure to slopes that have cornices overhead.
  • Cornice failure may trigger large avalanches.
  • Remember that the snowpack will be significantly different at higher elevations than lower down.

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.

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.