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Avalanche Forecast

Archived

Mar 4th, 2021–Mar 5th, 2021

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural and human triggered avalanches likely.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Sea To Sky.

With heavy snowfall and strong winds on Friday, natural avalanches are likely. Consider your ability to recognize and avoid terrain as travel in avalanche terrain is not recommended.

Confidence

High - We are confident the likelihood of avalanche will increase with the arrival of the forecast weather.

Weather Forecast

A powerful storm is impacting the region

Thursday night: Overcast, 20-30 cm of new snow, strong south wind with extreme gusts at ridgetops, freezing level dropping to 1100 m.

Friday: Overcast, 20-30 cm of new snow, strong south wind with extreme gusts at ridgetop, freezing level climbing to 1400 m in the morning and dropping to 1000 m by late afternoon. 

Saturday: Mostly cloudy, 5-10 cm of snow, light southwest wind, freezing level near 1100 m. 

Sunday: Mostly cloudy, 10-15 cm of snow, moderate south wind, freezing level near 1000 m. 

Avalanche Summary

Natural and human-triggered avalanches are likely on Friday.

There continue to be reports of both natural and explosive-triggered cornice falls (see this MIN report near Rainbow Mountain).

Snowpack Summary

As much as 30-50 cm of snow could accumulate above 1400 m by the end day on Friday. Strong south winds will contribute to rapid slab formation, making natural avalanches likely. The combination of wind and snow has the potential to weaken cornices, which can act as triggers on slopes below. 

In isolated areas with a shallower snowpack in the region, a layer of facets, spotty surface hoar, and/or crusts buried in mid-February may still be preserved. There have been no avalanches reported on this layer; however, large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow and wind have the potential to this deeper layer in areas where it may still exist.

The mid and lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Avoid all avalanche terrain during periods of heavy loading from new snow and wind.
  • Watch for changing conditions today, storm slabs may become increasingly reactive.
  • Use conservative route selection. Choose simple, low-angle, well-supported terrain with no overhead hazard.

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.