Avalanche danger is increasing with forecast new storms moving onto the coast.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
A series of Pacific disturbances are lining up to hit the coast over the next few days. Moderate snowfall amounts are expected above the snow/rain line, and valley bottoms should be warm and rainy. The freezing level should stay around 1200 metres overnight and then rise to 1500 metres on Friday. Saturday morning should be a bit cooler as freezing levels drop down to about 700 metres and stay below 1000 metres all day. Warmer air associated with the Sunday storm should push freezing levels back up above 1500 metres. Heavy precipitation, strong southerly winds, and high freezing levels are forecast for Monday.
Avalanche Summary
Thin pockets of windslab up to size 1.5 were observed on Wednesday. On Monday, warming and solar radiation triggered widespread loose wet avalanche activity in steeper, sun-exposed terrain. Large cornice collapses were also observed. Of note, warming also triggered a size 3.5 slab avalanche on the south face of Mt Currie. Similar action likely occurred on Tuesday. The gradual cooling trend will strengthen the upper snowpack making avalanches triggered by warming less likely.
Snowpack Summary
Variable new crusts have formed in the alpine and at treeline. Supportive crusts on solar aspects resulted in corn skiing in some areas. Breakable crusts were reported from Northerly aspects on Tuesday. Up to 30 cm of moist snow below crust on all but north aspects. Cornices are also reported to be huge and collapse has become more likely with daytime warming. About 50-90cm below the surface, you'll likely find a rain crust which formed on January 28th. This crust is widespread and exists up to about 2100m. Where it still exists, the mid-January surface hoar layer may be found between 130 and 200 cm below the surface. The combination warm temperatures and subsequent gradual cooling is making avalanches failing on these deeper layers unlikely.
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.