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Avalanche Forecast

Archived

Jan 30th, 2018–Jan 31st, 2018

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

Regions

South Coast.

Avalanche danger will rise in sync with new snow accumulations. Watch for both to increase over the day on Wednesday.

Confidence

Moderate - Forecast snowfall amounts are uncertain

Weather Forecast

Wednesday: Cloudy with flurries bringing approximately 5 cm of new snow, increasing overnight. Light to moderate south winds. Freezing level to 600 metres with alpine temperatures around -4.Thursday: Cloudy with continuing flurries bringing approximately 5cm of new snow over the day, increasing overnight. Light to moderate southwest winds, increasing overnight. Freezing level to 800 metres with alpine temperatures of -3.Friday: Cloudy with continuing flurries bringing approximately 5 cm of new snow to high elevations. Light rain below about 1000 metres. Moderate southwest winds. Freezing level to 1500 metres with alpine temperatures around -1 to 0.

Avalanche Summary

Reports from Saturday included one MIN submission detailing a near miss incident involving several members of a ski touring party on Hollyburn Mountain. Two skiers were partially buried and one was fully buried in a large storm slab that released from a steeper pitch below treeline. Please see the MIN submission for details. Other MIN reports from the region over the past two days have shown ski cutting easily producing storm slab results at the depth of each day's accumulations.Looking forward, areas that experienced heavy rain should see the snowpack quickly stabilize as temperatures cool. With that said, new snow that accumulates on this refreezing surface will likely form unstable new storm slabs before the new snow has a chance to form a solid bond. High alpine areas that haven't seen rain are on a different trajectory. Here, recently formed storm slabs will need more time to stabilize as they experience continued loading from new snow and wind.

Snowpack Summary

Light new snow amounts have begun to accummulate on the refrozen snow surface after heavy rainfall soaked the upper snowpack at most elevations over Sunday night and Monday. High alpine elevations in areas like Sky Pilot and the Chehalis Range may have seen thick new storm slabs develop over the same time period. Below these elevation-dependant surface conditions, storm snow totals from the past week reached 110-180 cm. The crust that exists beneath these recent snow accumulations is expected to have formed a solid bond to the overlying snow.

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.