New snow and wind starting overnight will develop storm slabs throughout the day. Pay particular attention to lee features in the alpine and treeline.
Storm slabs will develop throughout the day with new snow and wind. Be particularly careful 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 3-5 cm, 30-50 km/h southwesterly winds, low alpine temperature 0 C with freezing level around 2000 m.
MONDAY: Snow, accumulation 10-20 cm, 20-30 km/h southwesterly winds, high alpine temperature -2 C with freezing level going down to 1300 m.
TUESDAY: Cloudy with isolated flurries, accumulation 1-3 cm, 5-10 km/h variable winds, high alpine temperature -4 C with freezing level around 1000 m.
WEDNESDAY: Cloudy with isolated flurries, accumulation 1-3 cm, 10-20 km/h southweesterly winds, high alpine temperature -3 C with freezing level around 1200 m.
Recent heavy precipitation and warm temperatures produced widespread natural avalanche cycles at all elevations. Upper treeline and alpine terrain produced storm slabs and cornices to size 3 in most areas. At treeline and below saw wet loose and slab avalanche cycles to size 3 on all aspects, during the most intense rain and warming. Following the storm, avalanche activity has tapered off over the weekend.
Heavy precipitation over the last week has created a variety of surface snow conditions. Recent snowfalls with strong southwest winds have created pockets of dry snow at alpine elevations on north through east facing slopes. Precipitation fell as wet snow or rain below 2200m, creating saturated snow that is forming a melt freeze crust with moist snow below.
A crust that formed prior to the rain was observed up to 2000m. This is now buried up to 30 cm deep and may be breaking down at lower elevations.
Two buried weak layers of sugary, faceted grains sit in the middle and lower snowpack, at 100cm deep and 150-250 cm deep. The deeper layer was formed by heavy rain followed by a cold spell in early December. It is 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.
