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Avalanche Forecast

Archived

Feb 26th, 2021–Feb 27th, 2021

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

Regions

Sea To Sky.

Recent storm snow is likely to still be reactive, particularly in wind-affected terrain and on slopes that face the sun. Watch out for reverse-loading in exposed terrain.

Confidence

Moderate - Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.

Weather Forecast

FRIDAY NIGHT: Clear and cold. A wind event is expected overnight blowing strong northerly winds.

SATURDAY: Clear in the morning becoming cloudy in the afternoon. Mostly light winds switching from northwesterly in the morning to southwesterly in the afternoon. Freezing level around 700 m.

SUNDAY: Flurries. Moderate southwesterly winds. Freezing level around 1200 m.

MONDAY: 20-30 cm new snow. Strong southwesterly winds. Freezing level around 1000 m.

Avalanche Summary

On Thursday a couple of size 2 natural wind slab avalanches were noticed near Whistler in steep, northwesterly alpine terrain. A couple of human-triggered avalanches were also observed, one on north-facing terrain in the alpine and one on east-facing terrain below treeline. All these avalanches appear to have involved only the recent storm snow.

Snowpack Summary

Storm slabs formed by 20 cm of new snow and extreme east/southeast winds have formed touchy storm slabs that are expected to remain reactive to human triggers, especially in wind- and sun-affected terrain.

The new snow buried a variety of snow surfaces including wind pressed snow in the alpine, sun crusts on solar aspects, and a spotty layer surface hoar in some sheltered treeline areas.

Another 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

  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Extra caution is needed around cornices under the current conditions.
  • Avoid exposure to slopes that have cornices overhead.

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.