Confidence
Fair - Freezing levels are uncertain on Friday
Weather Forecast
The freezing level is expected to drop down to about 600 metres by Thursday morning. Thin high clouds combined with light southerly winds and warm temperatures are forecast for Thursday. Warm temperatures with freezing levels up to about 1200 metres are expected to continue overnight into Friday. Friday is expected to be warm with light winds and high clouds. A weak pulse of precipitation may move into the region on Friday afternoon bringing trace amounts of snow to higher elevations. The ridge of high pressure is expected to re-build again on Saturday, bringing cooler temperatures. Mostly clear skies may produce intense solar radiation during the day on Saturday.
Avalanche Summary
Soft slab avalanches up to size 1.0, some skier controlled and some skier accidental on steep NE facing alpine terrain. One natural cornice reported as size 2.5 on a NE aspect in the alpine.
Snowpack Summary
The new snow has developed soft slabs in the alpine and at treeline. Storm slabs that developed on the weekend have gained significant strength, as have the heavy storm snow accumulations from last week. Cornices should also be on your radar as strong southwest winds and steady snowfall have contributed to impressive development. About a metre down there are a variety of older snow surfaces that formed throughout January. These surfaces include facets, old wind slabs, and crusts. These interfaces have also gained considerable strength, but triggering may be possible with a heavy load in isolated terrain. Previous concerns about deeper persistent weak layers appear to have diminished. Snowpack depths at treeline are in the region of 260 cm.
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.
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.
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.