Spring conditions. While the freezing level remains high, wet slabs will be the primary concern.
Weather Forecast
On Saturday, light snow is forecast above about 1600 m, with light SW winds. A cold front arriving on Sunday brings 10-20 cm snow, with the freezing level falling to around 1100 m by afternoon. Clouds and a few showers may linger on Monday.
Avalanche Summary
No new avalanches have been reported. On Tuesday, explosives triggered a size 3 wet slab avalanche in the Duffey Lake area. The avalanche released at ground on a NW aspect at 2200 m and ran to valley bottom. A MIN report from Monday describes a close call with a size 2.5 wet slab avalanche on a NE aspect in the alpine on Hour Peak on the McBride Range traverse. A skier triggered the large avalanche that released down 30 cm on an old melt-freeze crust and propagated a fracture about 50 m wide. Most commercial operations in the region have finished their season and information is becoming sparse.
Snowpack Summary
As temperatures gradually cool through the weekend, loose wet and wet slab avalanches will become less likely. Storm slabs may develop at alpine elevations as the cold front passes through. At lower elevations, monitor the overnight freeze of the snow surface. If the snow surface does not freeze overnight or if the crust is only a few cm thick, the effect of daytime heating or rain will weaken the snowpack much more quickly than it would if there is a well frozen thick crust. Low elevation and thin snowpack areas have become isothermal.
Problems
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.
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.