Snowfall amounts overnight are uncertain and may be higher in western upslope areas. We are also unsure of when and where the sun will shine. Solar radiation on dry storm snow is a concern for increased avalanche activity.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
Moderate southwest winds and 3-5 cm of new snow overnight. Winds becoming strong from the west during the day on Saturday as a weak ridge of high pressure builds after the storm. There may be some sunny breaks Saturday afternoon, but more likely to clear overnight. Freezing levels bouncing between valley bottoms and 1400 metres. Mostly sunny on Sunday with light winds and freezing levels up to 1200 metres. Cloudy with increasing southwest winds on Monday.
Avalanche Summary
Wind loading followed by solar radiation resulted in a size 3.0 natural storm slab avalanche on a south aspect in the alpine on Friday. Another natural cornice fall size 2.0 was reported on Thursday from a north aspect in the alpine, it was also reported that this cornice did not release a storm slab on the slope below. On Wednesday a natural cornice fall resulted in a size 2.0 avalanche.
Snowpack Summary
Another 5-15 cm of new snow was reported on Friday morning. Each pulse of snow and wind continues to add to the wind slabs and settling storm snow from the past few days. About 40-60 cm below the surface, you'll likely find a melt freeze crust. This crust exists in most places except for higher elevation shaded terrain. In many areas there seems to be a reasonable bond between the crust and the overlying snow. I'd still keep an eye on this interface as it has become reactive on some features. Surface hoar buried in early January now lies up to 180cm below the surface and has become less of a concern. Possible triggers for this deep and destructive layer include a large cornice fall or significant warming.
Problems
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.