Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Mar 5th, 2022–Mar 6th, 2022

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

Northwest Coastal.

A persistent weak layer with feathery surface hoar crystals is buried 30-50 cm deep and can be found in sheltered treeline features and in the lower alpine. Warm temperatures will increase the likelihood to trigger avalanches on this layer. 

Confidence

Moderate - Uncertainty is due to how buried persistent weak layers will react with the forecast incoming weather.

Weather Forecast

Saturday night: Clear with cloudy periods, trace of new snow, moderate northwest wind, alpine temperature 0 °C, above freezing layer between 1300 m and 2000 m.

Sunday: Mainly sunny with cloudy periods, trace of new snow, strong northwest wind, alpine high +1 °C, freezing level dropping from 2000 m to 1300 m. 

Monday: Mainly cloudy with sunny periods, up to 5 cm new snow, moderate northwest wind, alpine high -5 °C, freezing level at 1000 m. 

Tuesday: Mainly sunny, no precipitation, moderate to strong northeast wind, alpine high -10 °C, freezing level at 500 m. 

Avalanche Summary

There have been isolated, skier reactive slab avalanches to size 1.5 on weak, feathery surface hoar crystals buried 25-50 cm at treeline and in the lower alpine. 

On Friday, a natural large slab avalanche was observed on a northeast aspect that likely released on the buried surface hoar layer. Skiers triggered small (size 1) avalanches on a northeast aspect on the same layer. 

A professional operation reported a slab avalanche being triggered by a wet loose avalanche from above on Thursday. And skiers triggered a size 1.5 slab avalanche from a distance away. It likely released on the buried surface hoar layer. 

Snowpack Summary

There's a lot going on in the upper snowpack. Careful assessment is recommended. 

There is a crust on the surface at lower elevations and on solar aspects at treeline.

Feathery, weak surface hoar crystals buried around February 26th are found down 25-50 cm, most prominently at treeline elevations. There have been reports of this layer being reactive to skier traffic. 

A thick crust buried in mid-February is now found down 60-100 cm. Though there has been little avalanche activity reported on this layer, it should be treated with suspicion. 

The lower snowpack is effectively bridged by the layers above, and we do not expect avalanches to be triggered in the lower snowpack at this time. 

Terrain and Travel

  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
  • Surface hoar distribution is highly variable. Avoid generalizing your observations.
  • Avoid travelling on slopes below cornices.
  • Firm cornices can pull back into flat terrain at ridgetop if they fail.

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.