Use increased caution during afternoon warming, especially on sun exposed slopes.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
A ridge of high pressure will keep the south coast clear and dry for Tuesday and Wednesday. The next frontal system arrives on the north coast Wednesday and should reach the south coast on Thursday. Current forecasts have the precipitation starting late Thursday. There is some model uncertainty regarding overnight freezing levels.Tuesday: Sunny, freezing levels am: 400-800m pm: 1700m, ridgetop wind: light variableWednesday: Mostly sunny, freezing levels am: 700-1000m pm: 1800m, ridgetop wind: light SW-NWThursday: A mix of sun and cloud, light scattered flurries possible, freezing levels am: 1000m pm: 1700m, ridgetop wind: light S-SW
Avalanche Summary
Reports from Sunday include isolated natural and human triggered slab avalanche to size 2.5 and widespread sluffing from steep terrain. The natural size 2.5 released on a north aspect slope in the storm snow up to 50cm deep. Natural size 1 wet slabs were reported on southerly aspects below 1700m. A skier triggered a small storm slab on a northerly convex feature in the alpine.
Snowpack Summary
The weekend storm produced 30 to 50cm in the north and around 30 cm in the south. Moderate southerly winds have formed wind slabs in immediate leeward feature in wind-exposed terrain. Below 2000m the new snow rests on a thin melt freeze crust on all aspects, with the exception being north facing terrain features above 1500m. Mild temperatures and solar radiation on Monday are likely causing settlement of the storm snow and melting of the snow surface on most slopes expect maybe steep north aspects in the alpine. The persistent weak layers from early March and early February continue to be a concern. The March weak layer of wind-scoured crusts, melt-freeze crusts, and/or surface hoar is reported to be down 60 - 100cm. The February crust/facet/surface hoar layer is now deeply buried down 150 - 250cm and may still be triggered by heavy loads like cornice falls or storm slab avalanches in motion. Long fracture propagations resulting in very large avalanches are possible with this layer. Avalanches releasing on these layers may step down to the ground during periods of strong solar radiation or warm spring rain.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.