Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Regions
Vancouver Island.
Main concerns: Loose Wet, Wet Slab, Cornice Fall.
Travel & Terrain Advice
Avoid exposure to all avalanche terrain during the warm temperature spikes accompanied by rain events over this forecast period. The thin/shallow early season snowpack will quickly lose stability as temps climb and rain saturates the snow.
In all but the alpine, the snow levels are still low, so be wary and on the look out for open creeks/holes and rocks/stumps etc lurking just below the surface.
Due to limited obs, spend a good amount of time doing your own snowpack observations and if unsure/unable… as usual avoid avalanche terrain.
Avoid wind loaded slopes where trigger-able slabs maybe (NW-NW aspects).
Avalanche Summary
No avalanche data/observations are currently available due to minimal field time (as it is the beginning of the season teams have not gotten out and about) and there has been limited visibility. During this forecast period, one can certainly expect to find evidence of a widespread loose wet avalanche cycle in the alpine and at treeline as a result of the big rain event (at all elevations) that happened Thursday Dec 13.
Snowpack Summary
A thin early season snowpack down low (below treeline). Zones of deep snow are found in wind loaded lee pockets in the alpine and treeline. Rain has saturated shallow areas right down to the ground and the majority of lower below treeline terrain is below threshold (to shallow to have avalanches of significant size). High winds have resulted in some cornice development in the alpine and treeline.
Snowpack Details
Surface: wet snow from Thursday nights rain event with new moist snow arriving Friday. Upper: rain saturate snow with a few thin melt freeze crusts. Mid: rain saturated snow from previous snow events. Lower: large crust from early season snow with a potential failure layer (of still dry snow treeline and above)mid crust, all bonded poorly to ground.
Past Weather
A large rain event Thursday night has saturated the thin early season snowpack. High winds during prior snow events has transported significant amounts of snow in the alpine and treeline elevation bands.
Weather Forecast
Multiple rain and snow events as temps and freezing levels fluctuate with steady moderate to strong SW to SE winds. Friday - Heavy rain and snow with strong winds during the day at all elevations. Temps and freezing levels drop overnight resulting in light to moderate snowfall. Saturday - Light-moderate snow fall in the morning with cold temps (-2 to -5). Snowfall increasing to moderate mid day then heavy overnight. Winds remaining moderate to strong SW to SE. Small reprieve between two big warm weather events. Sunday - Heavy snowfall continues into the morning potentially changing to moderate to heavy rain around noon. Winds remain moderate to strong.
Problems
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
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.