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 final regular forecast of the season and will expire on April 25.
Weather Forecast
Tuesday: Mainly sunny. Light south winds, increasing to strong at ridgetop. Freezing level to 3100 metres with alpine high temperatures around +4. Weak overnight cooling.Wednesday: Sunny. Light northwest winds. Freezing level rising to 3500 metres by evening and staying steady overnight. Alpine high temperatures around +7.Thursday: Sunny. Light south winds. Freezing level to 3600 metres with alpine high temperatures around +9.
Avalanche Summary
Decreasing traffic in the mountains has led to limited avalanche observations over the past few days, however a large (size 2) recent cornice fall from was observed in the north of the region on Sunday. It failed to trigger any slab.A few natural storm and wind slab releases were observed on Thursday, ranging from size 1-2.5. One of these was a size 2 slab triggered by a loose wet avalanche while the 2.5 wind slab was triggered by natural ice fall on a north aspect at 2200 metres. It featured a 45 cm crown fracture.Reports from Wednesday included an observation of a natural size 2 cornice release from a north aspect in the north of the region. Numerous natural loose wet avalanches were also observed on sun-exposed aspects in the Monashees.Observations from just over a week ago showed a pattern of heightened cornice failure activity.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 70-100 cm of mostly settled storm snow overlies another supportive crust existing on all but north aspects above about 2200 metres. This layer as well as the deeper (down about 80-120 cm) 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 as well as the possibility for triggering with a heavier load, such as a cornice collapse. Cornice collapses become more likely during periods of intense warming.Deeper persistent weak layers from December and January are considered dormant at this time.
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.