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: 500-1000m pm: 1600m, ridgetop wind: light SW-NWWednesday: Mostly sunny, freezing levels am: 500-1000m pm: 1700m, ridgetop wind: light SW-NWThursday: A mix of sun and cloud, light scattered flurries possible, freezing levels am: 1000m pm: 1500m, ridgetop wind: light S-SW
Avalanche Summary
Reports from Sunday include several human and explosive triggered storm slab avalanches up to size 2. These were typically soft slabs and released down 20-40cm. No natural slabs were reported but natural sluffing was reported from steep features.
Snowpack Summary
The weekend storm typically produced 30-50 cm of new snow but up to 80cm was reported. Below 2100m, on all aspects, this snow rests on thin melt freeze crust that was very reactive on Saturday. (The exception is north facing terrain above 1500m where the crust is not present.) The first part of the storm was accompanied by strong southerly winds that formed isolated wind slabs immediately below ridge crest. The mid March surface hoar/crust interface is down around 80-110cm. The bond at this interface is improving making it less susceptible to human triggering. The early-March crust/facet layer is down about 100-150 cm and the early February layer is now down close to 200 cm. These layers are mainly dormant at this time but still have the potential to produce avalanches in isolated areas. The lower snowpack is generally strong and well settled.
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.