Be alert to conditions that change with daytime warming. Danger ratings are likely to exceed posted levels if solar radiation is strong, especially at treeline and below.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Wednesday
Weather Forecast
Wednesday: Overcast skies with very light snowfall / Light southwest winds / Freezing level at 2200mThursday: Moderate snowfall/rain developing late in the day / Moderate southwest winds / Freezing level at 2400mFriday: Moderate to locally heavy snowfall/rain / moderate southwest winds / Freezing level at 1800m
Avalanche Summary
On Monday, numerous wet slab avalanches and glide crack releases were reported up to size 3 from South-West aspects. As long as temperatures are warm and solar radiation is high, I would expect more of this activity.
Snowpack Summary
We are in a classic spring melt-freeze cycle. The surface snow becomes moist up to 2200m on all aspect and to ridgecrest on sun-exposed slopes. Large cornices are becoming weak due to strong solar radiation and warming temperatures. Surface hoar growth and surface facetting is happening at night on high sheltered, northerly aspects. Isolated wind slabs exist in the immediate lee of ridge crests and terrain featuresA buried rain crust can be found down 50 cm and exists up to around 2100 m. Although unlikely, a large trigger such as a cornice fall or warming on a solar aspect could cause this layer to fail.
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.