Substantial warming and sun on Wednesday afternoon will destabilize the upper snowpack. Extra caution is required around and below cornices, and on steep sun exposed slopes.Check out this new video on warming: https://vimeo.com/160805040
Weather Forecast
A ridge of high pressure dominates for the rest of the week. Sunny and dry conditions are expected for Wednesday through Friday. Freezing levels are expected to reach around 3000m each afternoon, with cooling overnight. Moderate outflow winds are expected in the alpine on Wednesday and light outflow winds are expected for Thursday and Friday.
Avalanche Summary
On Monday, skier triggered avalanches up to size 1.5 were reported. The recent storm snow overlying a melt-freeze crust was reactive to triggering in wind affected terrain. Loose sluffing was also reported from steep southerly slopes. No new avalanches were reported on Sunday. On Saturday, wind slab activity up to size 1.5 was reported as well as loose wet avalanches up to size 1.5. We have now entered a period with daily melt-freeze conditions and the main concern for Wednesday will be during the heat of the afternoon. Cornices will become weak and could fail naturally. Loose wet sluffing is expected from steep sun exposed slopes.
Snowpack Summary
10-20cm of new snow accumulated over the weekend in sheltered areas. Over the weekend, southerly winds were loading north aspect leeward slopes. However, outflow winds on Monday are reported to be loading south aspects in the alpine while exposed north aspect slopes are being wind pressed and scoured. Large cornices are lingering and are expected to become very weak this week. Below the surface problems, the mid snowpack is generally well-settled throughout with no notable persistent weaknesses. On Monday, a sun crust is expected to have formed on south aspects. Melt-freeze conditions are expected to be widespread this week with very high freezing levels.
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.