Rain mixed with heavy snow and strong winds are expected during the forecast period. At upper elevations new snow will form touchy storm slabs. At lower elevations, loose wet and wet slab avalanches will be a concern on rain-soaked, steep slopes.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
MONDAY NIGHT: Rain. Precipitation 8-12 mm. Ridge wind extreme, south. Temperature +4. Freezing level 1500 m.TUESDAY: Mix of rain and snow. Accumulation 20-30 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1300 m.WEDNESDAY: Rain mixed with snow. Accumulation 30-50 cm. Ridge wind extreme, south. Temperature +1. Freezing level 1600 m.THURSDAY: Snow. Accumulation 35-45 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1200 m.
Avalanche Summary
Last Tuesday a skier was injured in a loose, wet avalanche on the North Shore mountains when the top 10-15 cm of wet snow released on the January 8th crust. On Saturday ski cutting produced loose wet sloughs in the top 5-10 cm of moist snow. On Friday explosive control produced a size 1 avalanche that released a 45 cm thick slab on a weak layer just above the January 7th crust.
Snowpack Summary
The upper snowpack consists of moist and wet snow and three prominent crusts (January 10th, January 8th an January 7th crusts) from recent warm weather and rain events. The most notable layer is the January 7th rain crust, which is now buried 40-60 cm deep. The bond at this interface will likely gain strength over time; however, professionals are monitoring this layer as it has the potential to produce large avalanches in isolated terrain.The snowpack depth at 1000 m is about 150 cm and many early season hazards are still present.
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.