Heavy rain, snow and wind will rapidly destabilize the snowpack. Sit out this storm, travel in avalanche terrain is not recommended.
Fresh storm slabs will form with heavy precipitation and warm temperatures. Greater loading will be found in wind loaded features, from southwest winds. Expect more reactive slabs where new snow sits over a crust.
Expect loose wet avalanches to be widespread below 1700m. Greater hazard exists in areas closer to the coast, where wet snow sits over a smooth crust.
A series of fronts moves inland creating warm, wet and windy conditions.
MONDAY NIGHT: 20-40cm with freezing levels rising to 1500m. Strong southwest winds.
TUESDAY: Light precipitation continues with 10-25cm expected above 1700m and rain below. Strong southwest winds. An additional 15-50cm overnight with freezing levels rising to 1900m.
WEDNESDAY: Strong and extreme southwest winds. A mix of snow and rain, 15-50 cm expected above the freezing level at 1900m, rain below.
THURSDAY: The front exits leaving clearing skies and no precipitation expected. Freezing levels rise above 2000m, with light easterly winds.
A widespread natural avalanche cycle is expected at all elevations with the incoming heavy precipitation and warm temperatures.
A natural slab avalanche cycle was observed near Squamish on Sunday. Avalanches were observed to size 3 on all aspects below treeline, and south facing aspects at treeline.
A size 2.5 naturally triggered slab avalanche was reported near Whistler, thought to have failed on the early December crust/facet combination. Small avalanches may step down to deeply buried weak layers such as this.
Heavy mixed precipitation and warm temperatures will rapidly create a wet and saturated snow surface with little cohesion. At higher elevations strong winds will load dense snow into wind affected features lee to the strong southwest winds.
Below 1200 m in parts of the region close to the coast, the last week's rain produced a hard melt-freeze crust. Expect this storm to break down any surface crusts and saturate the snow below.
This recent precipitation adds to the 100+ cm of snow that has fallen since January 1, which may overly sugary faceted grains that formed during the cold spell in late December.
Around 150 to 250 cm deep, another weak layer of faceted grains may be found above a melt-freeze crust that formed in early December. The layer 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.
