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Avalanche Forecast

Archived

Feb 25th, 2021–Feb 26th, 2021

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

Regions

Sea To Sky.

  

Recently formed storm slabs will be most reactive in wind affected areas at treeline and above. Be especially cautious as you transition into wind affected terrain.

Confidence

Moderate - Forecast snowfall amounts are uncertain.

Weather Forecast

  

THURSDAY NIGHT: Snow; 5-15 cm. / Strong, northwest ridgetop wind / Alpine low -10 / Freezing level 600 m.

FRIDAY: Mix of sun and cloud / Light, northwest ridgetop wind / Alpine high -5 / Freezing level 800 m.

SATURDAY: Mix of sun and cloud / Moderate, northwest ridgetop wind / Alpine high -6 / Freezing level 700 m.

SUNDAY: Cloudy with flurries; 3-5 cm. / Strong, southwest ridgetop wind / Alpine high -4 / Freezing level 1100 m.

Avalanche Summary

Explosive control work near Whistler produced storm slabs up to size 2 on Thursday. Storm slabs are expected to remain reactive to human triggers on Friday, especially in wind affected terrain.

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 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. The kind of layer that the new snow buried will affect how long slabs will remain reactive to human triggers.

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 50-80cm. 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 can awaken these deeper weak layers.

The mid/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

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.