New snow and wind starting overnight will develop wind slabs throughout the day. Watch for lee features in the alpine and treeline.
Wind slabs from new snow and strong southwest winds will develop throughout the day. Take care around wind loaded ridgelines and cross loaded features mid slope.
An advancing Pacific system will begin impacting the south coast ranges Monday morning with snow, wet snow and rain throughout the day.
SUNDAY NIGHT: Cloudy with isolated flurries, accumulation 1-3 cm, 50-70 km/h southwesterly winds, low alpine temperature -1 C with freezing level at 1500 m in the north and up to 2000 m in the south.
MONDAY: Flurries, accumulation 5-10 cm, 40-60 km/h southwesterly winds, high alpine temperature -2 C with freezing level around 1500 m.
TUESDAY: Cloudy with sunny periods and isolated flurries, accumulation 1-3 cm, 10-20 km/h southwesterly winds, high alpine temperature -4 C with freezing level around 1000 m.
WEDNESDAY: Cloudy with isolated flurries, accumulation 1-3 cm, 20-40 km/h southwesterly winds, high alpine temperature -5 C with freezing level around 800 m.
Recent warm temperatures and intense precipitation produced widespread avalanche cycles at all elevations. Natural avalanches to size 3 occurred in the storm snow at higher elevations where snow was less affected by rain. Lower elevations received significant rainfall and produced wet loose and slab avalanches to size 2.5. Following the storm, avalanche activity has tapered off over the weekend.
Mixed precipitation and warm temperatures over the last week have created a variety of surface snow conditions. Recent snowfalls with strong southwest winds have created pockets of dry snow at alpine elevations. Precipitation fell as wet snow or rain below 2000m, creating saturated upper snowpack that has now formed a melt freeze crust with moist snow below.
Two buried weak layers of sugary, faceted grains sit in the middle and lower snowpack, around 50cm deep and 80-200 cm deep. Early Decembers heavy rain and following cold spell formed the deeper layer of facets, that is now most prominent between 1700 and 2100 m. Avalanches on this layer are large, but sporadic and isolated. The most likely place to trigger it would be in thin, rocky snowpack areas.
The lower snowpack is well-settled and strong.
