Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Friday: Dry during the day with a mix of sun and cloud. Showers in the evening. Freezing level 2100 m. Ridgetop winds 20-30 km/h from the west. Friday night: 5 cm or so new snow expected. Winds light. Saturday: Showers possible. Some sunshine also likely. Freezing level around 1500 m. Calm winds. Sunday: Dry with a mix of sun and cloud. Freezing level 1900 m. Calm winds.
Avalanche Summary
A size 3.0 avalanche in the Harvey pass area on April 4th was reported to have started from a cornice fall and stepped down to the February deep persistent weak layer. Loose wet avalanches have been reported in the surface since then during periods of warming.
Snowpack Summary
Very warm temperatures over the past few days and high freezing levels with no crust recovery have resulted in moist or wet snow at all elevations.In the Smith Basin area there is 140 cm below treeline and the top 40 cm was found to be moist and well consolidated. The March crust below was decomposing at this location. The February deep persistent weak layer was down 80 cm and well preserved. Higher up at about 2300 metres the height of snow was a little over two metres. The March crust was not intact at this location and did not result in any shears in snow profile tests. The February deep persistent weak layer (DPWL) was down 100 cm and was a well defined layer of softer facetted snow below the hard (pencil) snow of the well settled mid-pack. Hard sudden collapse shears were recorded at the interface of the February DPWL. In the Elk Valley South the height of snow at 1900 metres was 430 cm. The snow was dry and loose above 1700-1800 metres and moist below where loose wet slides had released on solar aspects. There was a 2-3 cm supportive crust on Southerly aspects above 1900 metres, and no crust on shaded North aspects.
Problems
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.
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.