Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Friday: Expect continued flurries with accumulations of 10cm possible. Winds ease to light southerlies with freezing levels climbing to 1400. Saturday: Morning convection should give way to a weak ridge giving sunny breaks through the afternoon. Winds should continue light southerly with freezing levels reaching 1200. Sunday: Another weak system could give light precipitation and slightly increased winds from the west.
Avalanche Summary
Many windslab events have been reported up to size 2.0. These have been triggered naturally, with explosives and with human traffic. Isolated windslab events have triggered remotely. Crown depths are a typically around 60cm and over 100cm in some locations. Isolated, small loose moist events are running below treeline.
Snowpack Summary
30-40cm of new snow fell in the past 24 hours bringing storm snow totals to between 70-90cm overlying the March 26 interface. This has been accompanied by consistently moderate and at times gusty southerly winds, forming deep windslabs in lee locations. Cornices are huge, and will continue to grow with this weather pattern. The 0326 interface is a crust on all aspects except true north treeline and alpine, where small surface hoar is present in sheltered places. In snowpack tests, the bond of the new snow and the March 26 interface is poor, with easy planar results. At lower elevations the high freezing level has kept the new snow heavy and moist. Below the newest storm interface, last week's storm snow is well settled and bonded, with further strength gains deeper in the pack. In isolated locations the weaknesses from early February linger and the chance for a large, deep release is possible in times of rapid loading from new snowfall, rain or cornice fall.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.