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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

South Coast Inland.

New snow and wind have formed reactive storm slabs at all elevations. Conservative terrain choices will be critical to playing safe on Friday.

Expect hazard to be HIGH in portions of the region that receive 20 cm. or more snow Thursday night.

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system. Forecast snowfall amounts are uncertain.

Weather Forecast

  

THURSDAY NIGHT: Snow; 5-15 cm. for most of region except up to 25 cm. in Coquihalla area / Strong, northwest ridgetop wind / Alpine low -12 / Freezing level 500 m.

FRIDAY: Cloudy with isolated flurries; 0-3 cm. / Light, northwest ridgetop wind / Alpine high -6 / Freezing level 900 m.

SATURDAY: Mix of sun and cloud / Light, northwest ridgetop wind / Alpine high -7 / Freezing level 800 m.

SUNDAY: Cloudy with isolated flurries; 0-3 cm. / Strong, southwest ridgetop wind / Alpine high -3 / Freezing level 1400 m.

Avalanche Summary

No new avalanches were reported in this region on Wednesday. However, the incoming snow and strong northwest winds are expected to form storm slabs reactive to human triggers; especially in the Coquihalla area where higher snowfall amounts are expected.

Snowpack Summary

Storm slabs formed by 10-20 cm. of new snow and strong southwest shifting to northwest winds have formed storm slabs that are expected to remain reactive to human triggers; especially in wind affected terrain.

A weak layer composed of a crust, facets or surface hoar depending on elevation/aspect is now down 70-120 cm. This layer that was buried in late January continues to be noted in snowpack tests with mixed results. 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 lower snowpack is well settled and strong in most areas.

Terrain and Travel

  • Continue to make conservative terrain choices while the storm snow settles and stabilizes.
  • Use increased caution at all elevations. Storm snow is forming touchy slabs.
  • Expect slab conditions to change drastically as you move into wind exposed terrain.
  • Extra caution is needed around cornices under the current conditions.

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.