A wet, wild winter storm system with heavy precipitation, strong winds and mild temperatures is increasing the avalanche hazard. Avoid areas that receive heavy loading from snow and wind until the new snow has had a chance to settle.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
TONIGHT: Wet snow. Accumulation 20-30 cm. Ridge wind extreme, southwest. Temperature 2. Freezing level lowering to 1100 m.THURSDAY: Snow. Accumulation 30-40 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1000 m.FRIDAY: Snow. Accumulation 20-30 cm. Ridge wind moderate, southwest. Temperature near 0. Freezing level 1000 m.SATURDAY: Snow increasing. Accumulation 20-30 cm. Ridge wind light to moderate, southwest. Temperature near 0. Freezing level 900 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 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
At upper treeline and alpine elevations about 10- 20 cm of new snow has fallen and now covers the January 16th crust. Near treeline and below, rain has soaked the upper snowpack which consists of 15-20 cm of wet snow above three prominent crusts (January 10th, January 8th and January 7th) 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 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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.