Surface instabilities and cornice hazards should be firmly on your radar as you travel. Expect stability to deteriorate over the course of each day.This is our last regular forecast of the season and will expire on April 25.
Weather Forecast
Tuesday: Mainly sunny. Moderate southwest winds. Freezing level to 2700 metres withalpine high temperatures around +3. Weak overnight cooling.Wednesday: Sunny. Light northwest winds. Freezing level rising to 3500 metres and steady overnight. Alpine high temperatures around +4. Thursday: Sunny. LIght south winds. Freezing level to 3500 metres with alpine high temperatures around +7.
Avalanche Summary
Decreasing traffic in the mountains has limited avalanche observations over the past few days.Reports from Thursday included more evidence of the recent natural avalanche cycle described below, with several additional recent storm and wind slab releases to size 2.5 observed. Sun and wind were identified as prominent triggers.No new avalanches were reported in the Cariboos on Wednesday, but reports from the North Columbias included observations of numerous natural wind slab release from size 1-2 on north through east aspects in the alpine. A skier triggered size 2 storm slab resulted in a near miss. Another recent very large (size 3.5) storm slab was observed to have released on a large, wind-loaded alpine feature. Reports from just over a week ago showed a pattern of heightened cornice failure activity, with several releases triggering large slabs.Looking forward, a period of increasing warming, full sun, and warm overnight temperatures will be maintaining elevated chances of cornice and loose wet avalanche activity.
Snowpack Summary
A surface crust is likely to exist on all but north aspects in the alpine and is expected to undergo melt-freeze cycles with daily warming and overnight cooling. Below the surface, about 50 cm of settled storm snow from the past couple of weeks covers another supportive crust which shares similar distribution to the upper crust. This layer as well as the deeper (down about 100cm) mid-March crust are of limited concern concern after warm temperatures have promoted settlement and bonding in the upper snowpack. Any remaining uncertainty with regard to their strength is generally limited to high north aspects and the possibility for triggering with a heavy load, such as a cornice collapse.Deeper persistent weak layers from earlier in the season are generally considered dormant, but some deep layers, such as sugary facets at the base of the snowpack, are more prominent in the Cariboos than in other areas of the interior. Periods of intense warming are the most likely times for any natural release to occur and for cornice triggers to be more numerous.
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.
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.