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Avalanche Forecast

Archived

Mar 1st, 2021–Mar 2nd, 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

Sea To Sky.

Light snowfall and strong southwesterly wind will keep wind slabs fresh Tuesday. Older wind slabs exist on a variety of aspects and may remain reactive where they sit over facets.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

Monday night: 5-10 cm new snow. Freezing level dropping to 700 m. Strong southwesterly ridgetop wind.

Tuesday: Mostly cloudy. Freezing level 900 m. Light to moderate southwesterly wind.

Wednesday: Mix of sun and cloud. Freezing level rising to 1500 m. Moderate southerly wind.

Thursday: Mix of sun and cloud. Freezing level rising to 1700 m. Southerly wind increasing to strong.

Avalanche Summary

No new reports since Saturday when natural and human triggered avalanche activity quieted down but cornices continued to be reactive to explosives size 2-2.5. Minor pinwheeling was observed on steep solar aspects in the afternoon.

Snowpack Summary

20 cm of recent snow overlies a variety of old surfaces including facets, spotty surface hoar in wind sheltered areas around treeline, a sun crust on steep solar aspects and a rain crust below 1500 m. Recent wind of varying direction has blown this snow into wind slabs on a variety of aspects.

A weak layer buried in mid-February is composed of a crust, facets or spotty surface hoar depending on elevation/aspect, and is now down 50-80 cm. There have been no recent avalanches reported on this layer. Large triggers, such as an avalanche in motion, cornice fall, or intense loading from snow, wind and/or a rapid rise in temperature could awaken these deeper weak layers.

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

Terrain and Travel

  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Recent wind has varied in direction so watch for wind slabs on all aspects.
  • 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.

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.